Under your rational then you should be pro building a wall as currently illegal immigration is a default "racist" policy that encourages those from central America while discriminating against Indians and Chinese.
Build the wall and regulate immigration so more Indians and Chinese come relative to their world population.
Current immigration policy is racist, yes. It's dehumanizing to the people here illegally, and it's not fair by any means. My point is that legality is a fig leaf. When your definition for "legally" is "My ancestors got on a boat, and were white," it holds no weight.
"Hurr, durr, build a wall to keep them out", and "Keep America Christian" does nothing to resolve it. If you actually give a shit about either, then backing Trump (Or the other big names from the 2016 Republican line) is backing the wrong horse.
Even more ironically, two of the other candidates (Ted Cruz, and Marco Rubio) are the descendants of Cuban refugees... And any Cuban entering the US can immediately apply for permanent residency. No questions asked.
Strangely, they oppose the same privilege to people fleeing repression/drug cartels/terrible poverty in the rest of Central America.
Build the wall and regulate immigration so more Indians and Chinese come relative to their world population.