That's right: being offended is a skill. A skill that some people go to great lengths to develop. And since most memes are also jokes, this explains why the left can't meme. The art of being offended has grown to such a degree of specialization that those who are masters in it often seem to have no room in their brains for contradictory skillsets; you can't normally see the comedy in something, laugh at it and be offended at the same time because they are polar opposite emotional and social responses. The more you laugh, the less serious you being offended appears to be and therefore no one really does that. It's one or the other.
We all know which kinds of people have been gravitating towards which ends of the political spectrum. It's true that teams of writers with a lot of time on their hands can still make the late night clowns seem funny even though they are leftists but the average western liberal today is about as humorous as a medieval nun, with none of the good qualities. Sad!