I think the first time I heard a leftist reject the categorical imperative was a friend of mine who I met when we were activists for the 2000 Ralph Nader campaign and what was one of the most active local Green parties in the US for a few years. He was teaching a course in ethics at a local college and when I asked him about "how do I make better ethical decisions?" he gave me a spiel about how the left is on the side of the angels and the right is on the side of the devils.
On Mastodon I run into people like that all the time. If you confronted a rightist about, say, Pinochet's crimes, they would probably say it was justified, just look at what Lenin and Stalin did. They did it (and might even do it again) so we have to do it too. Many online leftists (like my ethicist friend) would probably say something to the extent that "it's OK that we do it but not OK when they do it" which is right up there with people who take Carol Gilligan too seriously.