How do I deal with accident meltdowns?

2-Step

DS understands he is not supposed to go in his undies, but when he has an accident, even a tiny one he has a complete meltdown. He gets really upset and cries and won't let me take his undies off. He is upset because he failed I guess. I try to make it no big deal and say- its ok, everyone has accidents, we'll try again. I keep it happy and upbeat and never get upset with him yet he still melts down. In a way I think it's good he understands that he wasn't supposed to potty in his pants, but I have to fight his undies off him and he is upset for about 5 minutes after that and cries and throws a fit about it so it is impossible to get him on the potty directly after an accident.

Has anyone else had this experience with PTing? What do you do about it? Do I just ignore it and try to get him on the potty anyway or should I let him sit in the wet undies until he is ready to let me take them off or try the potty?

I don't want to traumatize the poor kid, he is actually doing really well with it and has few accidents so I would like to keep going with it if we can get over this.