Personally I don’t have as much of an issue with when they’re poking fun at him per se, but when they denegrate or damage things he has clearly worked hard on and put a lot of passion into, that’s crossing a line for me. It becomes incredibly mean-spirited.
There are two examples in this compilation video. One at the linked time, and another at 6:33. Especially with how happy he is to see Leslie in the second clip until she destroys his art. It’s honestly heart-breaking. The pie to the face that came a little bit before that was also hard to watch and really felt mean. Dunno if that’s because of how cold and calculated it was (vs the more usual off-the-cuff comments), or because it was a physical act rather than verbal, or something else. But I didn’t like it.