again, i believe your fundamental misunderstanding lies in the fact that nobody demonises men as an entire group other than social media engagement farmers and ragebaiters. nobody actually believes that all men are predators, and consequently, nobody will unfairly attack "all men" for being abusers.
when people say "not all men", it is not as a defence for "men" - since there's no "attack" in the first place. it's used as a deflection when people try to tackle the deeper-rooted problems in society stemming from historical male-favoured inequalities.
"not all men" isn't a defence against a generalisation, since there is no generalisation in the first place (outside of engagement farmers and ragebaiters) - hence why i questioned your sources of media consumption.
again, people WILL look at this incident and think that therefore "all trans people are predators". this is a tangible, visible threat, which means that "not all trans people" is a valid defence.
different contexts, different meanings.