My 2 cents:
- In some cases there truly might be racism going on albeit concealed due to political correctness. The over the top rage officially over things other elected officials did previously where there was little to no protest leads some, including myself, at a minimum suspect the real reason for the rage is "he's not one of us" tribalism and that tribalism might involve race-based tribalism to some.
- In some cases there are simply honest opposition to policy. However, at least with me if I see emotionalism and/or driven by stupidity like a congratulatory fist bump is a secret Al Qaeda handshake, he hates white people or isn't a US citizen I begin to question its an honest opposition to policy.
- Most cases I think is "'world view projection," if that's a phrase. Example: The reason many republicans vote for conservatives is they honestly believe entitlement spending is out of control and think it ultimately harms the people it purports to help all while driving up the deficit. Since THEY vote for candidates due to opposition to entitlements, they falsely assume or "project their reason voting" that people voting differently do so because a support for entitlements when actually it's likely for other reasons such as possibly opposition to war, etc.
Likewise, many of Obama's supporters, especially in 2008 were not so much thinking about policy figuring all of DC is going to pretty much produce the same stuff anyway. Rather they saw the Presidency as a symbol of the ultimate American dream achievement. In light of the history of slavery, the 3/5 clause (or the reason it was instituted in the first place,) the Ku Klux Klan, segregation, lynchings, urban blight, etc., a chapter was turning in American society that to them was far bigger and more important than the percentage millionaires would pay in taxes on their capital gains or whether everybody had to get health insurance. What many of them did and still do is "project" their motives for supporting Obama onto those who oppose him and falsely assume the motive of their opposition is because of being opposed to the reasons they supported him. Making is worse is when you have the most ridiculous things many in the opposition complain about from being only "half black" to Shirley Sherrod to he's a Muslim who was born in Kenya and hates America, white people and the US flag and it honestly only reinforces that view.