Today half of these people would have been convinced by dudes on social media that real men don’t support this cause

Reagan and Thatcher were calling Mandela a terrorist after he had been released from prison. The western world was very much okay with apartheid then, much like they're okay with Israel doing a genocide today: because they can and will "do business" with fascists. Attitudes only shifted because it became economically unpalatable to "do business" with South Africa, largely because of boycotts.

Want to stop Israel? Make it cost the rich more to support them. Boycott, divest, sanction.