>Economics research says low wage immigrants are a net economic benefit, so it is in the interest of its citizens
Economics is not the only factor to factor into someone's interests. Everyone has things they value more than money.
>Also, I think the extreme poverty in parts of the world can justify help, just like how 1000$ is more to a poor person than a millionaire.
How does that justify help? It's not just like you help them to get on their feet and you're done. They and their descendants will live in your society for generations. Nobody is obligated to give them this at the expense of their citizens.
>No, immigration alleviates poverty as Americans are much richer than the average person. Why do you think so many people want to immigrate?
They want to immigrate here because wages are higher. However, there are only a limited number of jobs, and so flooding the job market with more people prevents natives from being able to find work, which is against their interests.
>I don't think it's a power grab by the left (open borders are not popular, as you can see right here) and that's irrelevant to the merits of open borders.
It's exactly like Roosevelt's Judicial Procedures Reform Bill of 1937, where he tried to pack the supreme court with justices favorable to his political faction, except this time they are trying to pack the US electorate. These people and their descendants overwhelmingly vote left.
>Well, I am against forcing racial diversity, so you can stay with your ethnic group/society in my proposal.
That's illegal in the United States. Every ethnic group has to live among every other ethnic group. Nobody can create societies that only allow people of their ethnic group to live among them, so it's not true that anyone can stay with their ethnic group, barring some serious constitutional reforms.