Whether your partner's actions were right or wrong, or normal or not, are general questions that each of us can argue differently. But what is NOT arguable, and should not be ignored, is that his actions hurt you. If he argues that you should not feel this way it is another example of his unwillingness to care for you, to be a friend. If he is so sensitive to another's feelings he should be sensitive to yours. Frankly, he sounds like a jerk.
He is also not very sensitive to the feelings of the woman he went to rescue, who from your own statements was only in "danger" of dancing with a poor leader, not a serial killer or sexual harasser. Most of my women friends would be more annoyed at him than at the supposed "bad" guy. They feel they are grownup, strong women who can handle problem men without interference. Plus, they might actually like the bad dancer, or at least feel sympathetic to him, and be willing to put up with his poor leading or lack of musicality or whatever for a few dances.
I occasionally see women being asked to dance by men who strike me as likely to make them feel uncomfortable by "teaching" them, often with continuous lectures while they dance, sometimes stopping in the middle of the floor to explain what she is doing wrong. The only reasonable help I can give them is to ask them to dance later, keep my mouth shut, and try to help them have the best time they can without referring to the "teacher." For all I know she actually appreciated the lessons, however unlikely it might seem to anyone watching. After all, I'm not a mind reader and am only guessing what her feelings are.
Laer Carroll
Maybe true as well... but I often see beginner ladies getting "led" through movements I know they don't know and afterwards ask them about it and more often than not they are quite excited to have done "fancy" steps with someone... 
