I don't have anything against them. I grew up with them and they are very sweet and loyal creatures (with the right training) but I have never really be able to understand them the way that I do a horse. I like horses more but I don't dislike mules.
I'll tell you more why I don't like "Casey" the mule. Well, he rubs his big ears on poles, was tied up to a trailer and kicked the wheel (then got severly hurt and blood was gushing out of his hoove, and desterbs you when you are riding other horses. Now can you see why I disike mules. But you have to admit "Casey" is kinda cute.
I don't know who Casey is, but it sounds as though he's not been well handled or trained.
As for rubbing his ears on poles, well I've never yet met a horse who doesn't rub some part of their body on poles/fencing etc. If he does it more than usual, maybe he has an ear problem or ticks in his ears. Has anyone bothered to find out?
I've known a few draft Mules and ridden one quite a bit years ago. She was wonderful to ride.
A well trained Mule, is no different from a well trained horse. Untrained either, can spell disaster.