Training would imply that it made effective activists, but activism from these quarters tends to alienate outsiders. It's more purity spiral than activism.

Well, no, I don't think training necessarily would make them effective given the context of academic activism. If the whole world would look like a college campus it might but there is such a big disconnect between the real world and academia that even the best trained academic activist ends up doing just what you describe. In some parts of society it has worked though, viz. the rise of the 'DEI' phenomenon driven in part by the infusion of academics into organisations who used their positions to bring in more academics of similar mindset while shunning those who did not subscribe to the desired narrative. Where it used to be said that it did no harm to let those silly students larp revolutionaries because they'd drop all that when they re-entered 'the real world' the truth turned out to be reversed in that they took all that ideological baggage with them into society.