Why the negativity surrounding Cormier?

I could be wrong, but I always felt that Cormier seemed to have to prove himself far more than other fighters had to until he was recognised, was always underrated even with wins against Monson, Silver, Mir, Barnett, Nelson, Gustafason.

I haven't seen much of his interviews or personality out of the ring, so am I missing something? Has he got an bad attitude or something? Just seems the guy has been bashed and underrated continuously when he's a beast of a fighter.