Namely, that bigotry is not a natural human trait. Fear of change and the unknown is, and this can be construed as bigotry, but they are not the same.
I also believe that actual bigots are vastly in the minority in the US.
I further believe that no one group of people has a monopoly on bigotry. It is in general evenly distributed across all artificial divisions, as are all other negative personality traits.
In my mind, it then follows that, if someone believes a majority segment of those who oppose Pres. Obama do so because of his skin color, they are bigoted against those who oppose Pres. Obama.