Michael specifically mentions in an older video with Dalton brainstorming things they could do about Trump. I don't recall ever seeing a YC video where Garry leaks any political affiliations, though I don't follow him on social media.
I don't recall the specific Dalton + Michael video, and it's not important enough for me to dig up, particularly if Garry is politically outspoken on social media. I'd prefer to believe YC is still a neutral player, but the amount of ring kissing from the big valley VCs makes suspicion rational.
