Is Trump racist for building a wall?
A: It could be, depending on your motives. If your motive is that you think all latinos are inferior to whites, and that's why you want to keep them out, then it could be racism. When FDR started it, or Bill/Hillary Clinton's campaigned on it (calling it a fence), or Obama demanded better border security, the Democrats didn't call it racism. In order to show it is racism, you'd need to show that Mexicans are a race, and that Trump doesn't like the entire Mexican people. But racists don't usually hire, hug Mexican voters, and celebrate lowering latino unemployment. Anyone who cares, knows that Trump is fine with legal immigrants (though probably less so than I am), just not illegal immigration. So unless you have evidence against the more likely scenarios, assuming the worst shows the bigotry of the accuser more than the accused. But that won't stop/slow the media left from doing it.
The Mexico-American border is the most heavily crossed border in the world, both legally and illegally, and has a rich history of the Democrats promising to fix it or illegal immigration, then undermining it. The Democrats can only win elections if they have the young, dumb and disenfranchised voting for them -- so they do everything they can to make sure that base (including uneducated illegals) can get in, and be exploited, and exploit our system. That guarantees them money/power.