Not sure it rises to the level of a slur but the poster in the image does have a point about it being a reductive term for MLs that papers over the accomplishments of socialist movements around the world.

I'm actually okay with this. Libs have gotten way too comfortable using this word and I'd like it if they were shamed as a result.

Given how it has been used to denigrate and mock communists from the global south, it might as well function as one.