There are two kinds of "immigrants," i.e. those that went through the process that awards permanent residency legally and those that are in the United States illegally ignoring American law.  Now we have a real problem because the world has many billions and many of those would be happy to live in the USA.  If we open our borders like some apparently want, our population could literally double in a few years.  So some "support" the illegals effectively teaching folks outside the US that once illegally in the US, they have it made.  Not a lot of thinking going on by those who instinctively say give the illegals anything they want.