By whom exactly? He has a large fan club on the internet and uses modern social network very well but I don’t think there is a wide consensus that he is better than Kasparov at his prime. I personally don’t believe him to be better than neither Fischer nor Botvinnik but that’s only me and is impossible to verify anyway.

And no, his opinion against his own opponent after suffering an embarrassing defeat poorly playing with white doesn’t hold much credibility.