Criticism of a guy with Aryan Brotherhood tattoos is invalid because it expended time that could have been used to Do Things™ such as church-style community activism

Why is that type of criticism chiefly directed at people who try to refine a theory of action, point out opportunists, and place things in historical context? Is this not a perfect example of the way it can be used to browbeat people belatedly attempting to hold the line against fascism?