I think you fail to understand how little sway pro Palestinian crowd has or how little it matters to the key swing voters that Harris is trying to get. It's like trying to get Harris to adopt Bernie Sander's policies.
Harris is appealing to centrist voters right now. Most of the centrist voters in key counties/states don't care about Gaza. They couldn't find it on a map if you gave them 100 chances. Statistically most of them are Christians and probably even Evangelicals.
So no, that's not how harm reduction works. You can certainly make your voice heard through petitions, rallies, calling their office, etc in the hopes that the candidate shifts their position. But ultimately harm reduction involves holding your nose and voting for the lesser evil(the candidate likeliest to do the least bad things according to your beliefs). Harris is a no brain pick when compared to Trump. If Bernie Sanders was a Republican and running against Harris in an alternate universe then Koya and Snub voting for that Bernie candidate would make all the sense in the world and I would completely understand.