I think it's less about the immigrant situation in particular, and more about the way the new President is wielding his power blatantly in front of a nation who is _extremely_ divided when it comes to their opinion of him. It's not that those other issues are less or more important, but that they have a much less identifiable perpetrator. A prominent cause is more easily reducible.

It's a cry for someone or some organization to help guide us back to center. The ACLU just happens to be one of the best positioned organizations to fit this situation.