Yes, actually. A politicians first job is to get elected. It doesn't matter how good their policies are if they just never get elected.
So if the anti-genocidenvoting block was actually a thing that voted reliably, then politicians could cater to those people instead of the pro Israel crowd.
And even ignoring that, when the choices are the guy that was somewhat pushing back on Netanyahu and making some effort to help Palestine, Vs the guy who is enthusiastic to go all in with Netanyahu, and cleanse the entire region so he build property their and make money and gave Israel the go ahead to start several all new wars. And we get one of those two options no matter what, then not voting is implicit support for the second, much worse option.