Not all instances should defederate from lemmy.ml. However, it is an issue that everyone commenting on every post across every community on that whole entire instance must essentially conform to all of their ideals - or else be banned from all of those communities, not merely the one with the "offensive" statement. You cannot say anything truthful about Russia, China, Ukraine, Uyghurs, Taiwan, Israel, Palestine, Gaza, etc.
Imagine if we were on Reddit and could not say "fuck spez", or we were on Linux but for some reason were still forbidden to say "I prefer not to use Windows today, so thank you but no thanks". Those communities on Lemmy.ml are held hostage to people if not agreeing then at least going along with whatever party line BS that the admins want to uphold. Moreover, at any time they could add whatever their wanted to that list.
Perhaps there will come out a fantastic Linux distro that would revolutionize Linux accessibility - but if they say no, then nobody can access any of the communities there unless they (at the very least tacitly) agree to not so much as mention its name, or that it exists, or anything else about it. This is a hypothetical but I hope you also see the connection to irl: it doesn't matter what those admins are banning people for, it matters that they have set themselves up as the arbiters of "truth(iness)", and decide what can or cannot be discussed in their platform. Regardless of which community it is in.
Most of us came here to get away from such, only to find that it is here as well.
Do as you please, but I hope this helps explain just some (and this probably isn't even fully half of it yet!?!?) of why people are judging the instance. Over time, more and more communities will move off of the instance - the main reason it hasn't happened yet I think is that version 0.19.3 (iirc?) promised to allow user blocking, which people see now how weak it is plus with 0.19.4-5 it actively got even weaker. Only defederation is left to even consider. Which won't happen quickly, but e.g. dubvee.org and lemmy.cafe both have already done so, and I imagine others will follow suit before too awfully long, with the amount of vehemence people feel about the situation.