Well, harmful people may be harmful on their alts and they deserved to be reported. Once harmful behavior is shown reports will be made and the profile will be banned.
Making alts isn't the bad thing here. The bad thing is to use those alts to make negativity. Many of the willows alts don't try to spread negativity, instead they are just trying to contribute to actual topics and get banned for a few posts.
If there is no reports made and there is no negative behavior, there is no need to even report them and get them banned. Having a profile with 0 negativity despite having a history of being violent is the equivalent of a normal law-abiding user, until the former breaks site-wide rules that of course will get them banned, sooner or later.
Mesmer being MgtowDemon isn't the bad thing here, even if it is true. If you are reporting non-ban-worthy accounts out of bare speculation or reporting random people for no reason, then I don't know who being more detrimental to the site here.
Are most people OK with Mesmer posting things? YES. So even if Mesmer is an illegal alt, it impacts nearly nothing. Concluding that the mods are cowards just for a not-yet ban-worthy account is in itself fallacious.