If you'll allow a pretty silly continuation of your metaphor, I think a lot of those people who don't like either option of "pull the lever" or "don't pull the lever" would rather move people from the track and let the trolly go on than just sit there and watch people die. Sure, there's people who would rather take apart the tracks so people can't continually be bound to them, and there's also people who would rather take apart the train, but I think the most vocal critics would be fine with going back to holding their nose and voting for Biden if he just stopped supplying arms to perpetuate a genocide (as well as stopped vetoing UN resolutions for cease fire). That's why there's such a vocal push to no longer be complicit in genocide- to get Biden to take people off the track (there will still be people on the track for a while since we've sent enough weapons to last a while and even after our weapons run out, there'll still be people on the track, but at least we won't be putting them there). But it's honestly exhausting seeing Biden flirt with absorbing ex-nikki haley voters rather than even look at the left to help him stay in power.

Though that being said, there's probably more Nikki haley voters than leftists in this country (I say this as a leftist), so I guess it's a fine strategy if his goal is to win, but expecting leftists and antifascists to be happy with our continual march rightward is silly.