If that is the sum total of what the guy did then it would be an excessive reaction to write him off IMO. I’m assuming, based on the noise it is generating, that he got defensive or doubled down rather than accepting the criticism and trying to grow from it. But I don’t know.
I agree that the left gets incapacitated by allegations of -isms and it is absolutely not a good thing. My worry is that we get into a situation where we cannot criticise a particular person or group because they are “good socialists”. What bad things do we let slide in the name of the greater good?
My strong opinion is that we (individually and the left in general) need to get a lot better at taking criticism, particularly from minority groups or marginalised people. And part of that, unfortunately, is to accept that we might have to put up with a deeper level of mistrust than we feel we are personally accountable for because of damage done by other people on the left.
I could ramble on more but perhaps I should start a thread not related to the NIP as it would be getting a bit off topic.