There are plenty of people that defend or deny the crimes of ML states. The MLs who don't defend or deny the crimes of ML states usually don't stay MLs. A big part of the entire ideology is not disagreeing with the party line in public. Democratic Centralism necessitates that you don't disparage what the party internally decides on. The attitude of most western MLs is one of not letting their team look weak, which usually leads to denying, defending, or using whataboutisms to downplay the bad things done by those states.

I acknowledge the terrible shit done by America and the Democratic party, but I still insist Americans should vote for Democrats over Republicans in elections. This is because people need to make the most out of the system and situation they have to work with. I don't think of Chinese citizens as tankies for supporting the CCP or Soviet citizens who worked within the confines of their government. That's the system they had or have, so they do what they have to do. This isn't the case with western MLs; not legally at least.

Western ML communities are basically cults that isolate you from outside friends or allies, encouraging you to push away those that question the ideology. You are free to leave, but through cultish tactics, they do everything they can to keep you in. If an ML acknowledges the crimes of ML states and the fundamental weaknesses in the ideology, tankie MLs will marginalize them from the group, coercing them to become tankies or leave. The non tankie MLs get driven away, or become tankies. It isn't a stable state, as they will always fall one way or the other.