Many people who think the illegal aliens should be deported don't think they deserve or have the same right as Americans. Non-citizens' well-being just isn't as important a consideration. That is a prejudiced attitude, no doubt about it, though it's not necessarily racially motivated.
But there is a flip side. Many proponents of illegal immigration (yes, there are many) aren't so gung-ho about increasing African immigration or ending forced repatriation of Haitians. These people show, with their actions, that they think Mexicans deserve special consideration over Haitians and Africans. Is that any less bigoted--esp. when you consider many of these "Mexicans-first" people are Mexican?
Suppose someone said only people from England and Spain should be allowed to come to the U.S. while Swedes and Italians should be blocked. Would anyone doubt--despite the pro-immigration credentials--that position is discriminatory?