I’m guessing the joke is that third party voters ignore the trolley about to go down one of two paths, instead deciding to stand next to a short piece of track connected to nothing with no trolley on it, so they can pretend the imminent disaster happening on the other track isn’t real
And there’s also a contingent of people on the trolley who are trying to get it to slow down, working their asses off to improve long term actual outcomes in the real world, whether related or not to the little lever, and the guy standing next to the empty disconnected track is claiming to be one of them and saying you must be against them and how dare you, you person-running-over-enabling monster, if you say anything against his strategy.