Zionism is the belief that Israel has the right to exist, and that Jews have the right to live in Israel.
If you are against this, your views are quite extremist and it is hard to find understanding and accommodation, particularly among fellow Jews.
It's a bit more complicated than this. Israel militarily occupies Palestine. And they institute an apartheid system that is unfair to Palestinians, denying basic rights to Palestinians -- they can take your property, they can restrict your travel, they can strangle your economy. And they do.
You might say Israelis deserve to live life in peace, but shouldn't Palestinians as well? The state of Israel was carved out of Palestine, so can you blame the original inhabitants of the area that they feel something was taken (and still being takene) from them, and can you blame anyone from sympathizing with that perspective? You don't have to be anti-Zionist to at least empathize with the complexity of the situation & understand that the state of Israel has enacted some very problematic policies and conducted problematic actions. I don't think it's fair to just call it extremist by any means.
There are also levels to everything. Some folks are unhappy with the Israeli state as it exists today, but by saying they're anti-zionist & "Israel shouldn't exist" they typically aren't advocating for murder, they're advocating for a one-state solution so that inhabitants of Palestine/Israel can get democratic representation & equal rights. Again, not a crazy take.
This is in fact a crazy take. It’s not quite advocating a shared state for Nazis and Jews level of crazy but it’s certainly getting there. Palestinian nationalism is based on being anti-Israel in much the same way anti-colonial or anti-metropolitan nationalism is. See Catalan, Scottish, Irish or Welsh nationalism.
Palestinian nationalism is much more like Irish nationalism than any of the rest of those in that people have killed for it in large numbers.
When people say something really stupid you have the choice of believing they’re lying or stupid. One staters are some of one and some of the other.
And let's be real, Israel is in control here. They have a modern military and are the occupiers. The way they've gone about this is the cause of much violence. Imagine the desperation of living in an apartheid state: feeling that you are not being represented or fairly treated by the systems governing you. Imagine being treated differently from your neighbor because you're not a citizen, and you can never be one because of your race and religion. It's totally fair to call them the oppressor in this situation because what the heck are these loose disorganized confederacies living in occupied territory going to do? They don't really have power to change the situation.
This is roughly like advocating for ending the Russian-Ukrainian conflict by advocating for a one-state solution where the inhabitants can get democratic representation & equal rights.
Also, the one state solution is not advocating for Israeli annexation of all Palestinian territory -- it's advocating for the view that Israel has already de facto annexed Palestine, and that the current Israeli government is implementing a brutal apartheid that needs to end. Calling the whole state something new, giving everyone citizenship, and electing new leaders won't solve everything but it's a valid perspective to have.
“Anti-Zionists view it as a colonialist, racist or exceptionalist ideology or movement.”
Characterising the groups views as believing Israel should not exist seems disingenuous.
"Advocates of Zionism view it as a national liberation movement for the repatriation of a persecuted people to its ancestral homeland. Anti-Zionists view it as a colonialist, racist or exceptionalist ideology or movement."
You do not get to tell other people what their views are. In the first place, questioning what has in practice meant "buy some tanks and go oppress the natives" is not something spoken of positively for literally any other country doing it. But when it is Israel, pointing out that humans have (and should have) rights somehow means that you hate all Jews. Ridiculous. Rather it is the reverse: Understanding Jews and their historical circumstances should give you a renewed respect for human rights and how important they are.
They are judging people's views, not telling them what to think. It's fine to believe what you want about other people's views. You do not control other people's minds.
When "Zionism" also means that Jews can create a "Jewish State" that discriminates against non-Jewish indigenous inhabitants (e.g. through a racist "law of return") - this is a big problem.
That land must be shared..
However if you were to right now offer the people of Palestine a guaranteed peace with a two-state solution based on the Oslo accords they would overwhelmingly vote to accept it. I don't think you could say the same of anyone who describes themselves as a Zionist. Though I don't know how widespread that belief is among the Israeli population, it's entirely likely a similar majority in Israel would be satisfied with such a solution.
Zionism is about the right of Israel to exist as an explicitly Jewish nation state. Being anti-Zionist does not mean you believe Israel should cease to exist, unless you define Isreal only in terms of ethnicity and religion.
> If you are against this, your views are quite extremist and it is hard to find understanding and accommodation, particularly among fellow Jews.
That's a fairly recent development in the grand scheme of things. Prior to the formation of Israel, Zionism was frequently contrasted with Bundism. The Bundist idea was that the "Jewish nation" is inherently a nation without borders and that Jews should organize internationally wherever they are. Bundists still exist but when Israel was created a lot of Jews adopted a more Zionist stance as the existence of Israel pretty much forced their hand in the debate.
There are still many good arguments against Zionism even now that Israel exists, especially from the point of view that just because Israel wants to be a "home country" for (certain) Jews, many Jews already have a home country elsewhere and identifying Israel as their home country only plays into the hands of antisemites arguing they're "foreigners" who don't belong in the country they were born into.
In fact, many white nationalists in the West use Zionism as a talking point to support their demand for white ethnostates: if Jews can have Israel for Jews, why can't "ethnic Germans" have Germany for "ethnic Germans", etc. The arguments of course get increasingly incoherent with places like the US where pinning down an "original white ethnic identity" requires a fair bit of mythologizing.
Arguably, Israel as a "Jewish state" is a late project of 19th century European nationalism, which largely fell out of fashion after WW2 with the increasing globalization of trade and industry and the softening of national borders through common trade areas and projects like the European Union. The perceived necessity for a "Jewish home country" was accelerated by the Holocaust (and the refusal of Allied countries to take on Jewish refugees until it was too late) but the "Jewish consensus" of universal support for Zionism is more manufactured than authentic and Israel has become as divisive as it has become unifying (e.g through the disregard towards Yiddish as a Jewish language, racism towards non-white Jews, prominent individuals like Netanyahu engaging in Hitler apologism, etc) even if you don't consider issues pertaining Palestinian Arabs.
EDIT: Since most people are likely unfamiliar with the term, here's the Wikipedia article on Bundism:https://en.wikipedia.org/wiki/Bundism
Although primarily a historical movement pre-dating the formation of modern Israel, Bundist movements still exist in many countries today and tend to be especially popular with Jewish socialists (who tend to be critical of Israel which they often perceive as an imperialist and colonialist project).