This argument is profoundly weird. There are more people living on Manhattan than in Montana.

By far the most common existing model I've heard reference for a theoretical white ethno-state is Israel. Non-white people would not be banned from participating in it, but it would exist with a mandate to serve the interests of a particular culture and people. In the same way that Jewish people can apply for automatic citizenship in Israel, people with European heritage would be given incentives to migrate and participate in the state. Of course, Israel did not come into being without war, and most white nationalists that I've seen anticipate future wars, but nearly all of them see an ethno-state as a response to war and destabilization rather than a cause of it. Most also advocate a peaceful migration of populations rather than forced or violent ones.

The most common historical model for white nationalism is the United States itself. The country was not founded to serve the needs of every race and people equally, but the particular interests of white British colonists. Eglitarian movements participated in the creation, and the abolition movement pre-dates the founding of the country, but the overall effect of the specific policies and laws enacted prioritized the interests of white people, and policies implemented into the 20th century and even some today reflect this clearly. If we deny that countries like the USA were originally patriarchal white ethno-states that eventually allowed equal particpation for women and minorities after centuries of advocacy, we lose touch with history. Most people still recognize this, but it's often ignored, most often by people with center-right politics who would prefer that history more closely resembled the present. But those old traditions still have a strong pull on people, and the only way to argue against them is to admit that, for all of human history, most people have preferred to live around people who look like them and share a common culture. Moving toward a different type of social organization is extremely difficult and can't be done without discussing openly why people have tended to prefer it. Look at centuries of failed attempts at communes to see how difficult it is to get people to act against their natural inclinations.

There are plenty of people with violent tendencies that would welcome ethnic wars. This is not restricted to white nationalists, but includes all sorts of people, and their motivations often intersect with other movements. The New Zealand shooter, for example, considered himself an "extreme Green" and killed people both because he interpreted them as a foreign invasion and because he wanted to oppose migrations that would lead to rises in population. This in itself does not mean environmentalism or advocating population declines is a dangerous movement. The particular aspects of his ideology advocating violence are dangerous, which is why there are rules specifically addressing calls to violence.

This ban which states that expressions of racial pride is allowed but bans advocacy for a nation-state which prioritizes the needs of an ethnicity, and only if that ethnicity has light skin, raises some interesting questions. If the model for white nationalism is Israel, a nation that serves as the homeland for a particular, majority white people, does support for Israel qualify as white nationalism in this context? I'm sure Facebook won't interpret it that way, but there are stong anti-Israel movements that consider support for Israel over Palestine to be an expression of racism. How we handle these kinds of things moving forward is not at all clear.

Jihadis don't do it implicitly they do it explicitly.