[mrdependable]

People support things that sound like a good idea to them, or that have been sold as a good idea to them, especially if they think it won't negatively affect them. It's easy to be pro open borders when you can't see how it would negatively impact you.

You say it clearly does not benefit them, but the problem is that nothing is really clear or obvious about it. There are a lot of different puzzle pieces, history, and order of effects that need to be considered which most people don't.