...Leaving is not running away, it is merely choosing a better option.

There are many good aikido teachers out there, and they do not treat their students like crap. You mentioned uchi-deshi being treated like crap in the old days. Well, I'm pretty sure that being treated like crap didn't make them better at aikido. It was merely the way things were done back then, particularly in Japan. We are talking about the period of time around WW2 when young men were expected to crash their planes into the enemy for the good of the country, and doctors were expected to perform vivisections on POWs. At that point in time, a lot of people were treated like crap with no good reason.

Your teacher may expect you to train hard, even to the point of exhaustion. He may expect you to make sacrifices in terms of your free time. He may challenge you to face your fears. What he may not do is yell at you, insult you, and take away your self-esteem. That is abuse, and there is no excuse for it.