> you have to convince them it's good for people working in ad tech to oppose ICE.

Yes—and one of the tools we have for that is shunning.

If enough of us who are appalled and disgusted by the state of things, and the people who willingly lend themselves to creating said state, make our disgust with those people known, it can lead to some of them choosing to act differently, because they care about being thought well of by their fellow techies.

I agree with what you're saying, but shunning has to be selective to be effective. People have to believe that you won't shun them if they avoid the terrible things you're trying to stop. It's too much to simultaneously beef with ICE, adtech in general, Tesla, $8 donuts, and anyone who lives in a trendy neighborhood.