Yes, the GOP has made itself the party of unalloyed white supremacy. And Latinos know it.
For Latinos moving to the Dems, the issue is immigration. This is personal and moral. Every "illegal" immigrant is the uncle or niece or spouse of someone "legal." Whatever other priorities Latinos may have, they will resent for a very long time demonization of family members. And the Republican base eats up demonization.
Roberto Lovato has described how Republicans who tried to rule through race baiting turned California Democratic:
Little noticed findings from last Tuesday's exit polls suggests that immigrant bashing isn't even a smart tactic to win among the existing, majority white, electorate. Nationally, 57 percent of voters think most of the undocumented should "be offered legal status," while only 38 percent think the undocumented "should be deported." Border states like California and Texas were slightly more sympathetic to legalization. Even Arizona, which passed anti-immigrant initiatives, was only one percentage point less supportive than the national average. Most U.S. citizens understand the country needs the people who make up the undocumented work force and want elected officials to get on with creating a path to legalization.
If Democrats want to win and keep the Latino vote for a generation, their choice is clear -- become the party that works for a path to legalization and reap the credit. The party that puts its weight behind border fences and xenophobic laws will create a generation of young brown people who will remember your insult for a long time.