Probably the cruelest excuse you can make about your horse is to say this about his slightly poor or quirky behavior...his slightly abnormal reaction...his somewhat odd reflex:
"It's just the way he is. He's always like that."
Why is is cruel? 99% of the time he's trying to tell you something isn't quite right. He's a little bit stoic (or maybe a LOT stoic). It's easy to write it off. After all he's not hurting you or his grooms and it's not THAT aggravating...you can put up with it because he does his job well. He wins ribbons, good ones.
If he's not stoic, you have already called the vet and had it checked out because he told you loud and clear that he's in discomfort.
It's not the 3 legged lame horses I worry about. They get the attention. It's the ones who win ribbons, give lessons, cause no trouble that no one bothers to get checked out that I worry about. The good horses.