There’s a long history here, which is bound up in everything from the two sides’ different definitions of patriotism – “my country right or wrong” versus “I want to improve my country because I love it” – to religion to militarism to cosmopolitanism to a thousand other things. Every American presidential campaign, on some level, is about the Republican trying to frighten people into believing that the Democrat doesn’t share “your values” and the Democrat trying to reassure people that he does. So, for conservatives, Obama is not just a guy whose views they vehemently disagree with. He’s an ideological Typhoid Mary, a carrier of unknowable and barely comprehensible infections.
That is qualitatively different from liberal hatred of Bush. It is also, to be blunt, paranoid – because it’s rooted in metaphorical narrative far more than in fact. And that means facts can never win an argument. Obama could leave office in January 2017 with the capitalist economy roaring and American power and security enhanced and these voters would still believe we’d escaped state ownership of everything and one-world government by a whisker. It’s been part of the psychology of the American right for decades, and it sure won’t be dissipating as long as Obama is in office.