It is not trolling if and when I provide that proof.Im sure he's trolling.
Liberally calling people racist demeans those who are actually racially abused.
If the racist refuses to accept that proof, and cannot provide any other explanation other than mere denial, or distortion of others' comments (for which they are not unknown to do), the description applies.
There does not have to be an act of racism for someone to be a racist.
If their beliefs are inherently and fundamentally racist, they are racist.
When the mood and culture of the forum is dominated by such people, the forum appears to have that mantle of racism.