I think the best way to put it is that protests can be effective only when they present a credible threat of some sort against the people who have the power to make changes to whatever the protest is about. That threat may be direct violence, it may be electoral change, or it may be something else, but a credible threat of some sort is absolutely required.
Protesting against Israel, therefore, is of little use in most situations. The protesters pose no credible threat to Israel, so their decisions aren’t going to change. And the protesters generally are not representing much of a credible threat against their own governments either, so their own governments are also not moved to change.