The problem with that (not verbalizing anger) is that it sends the wrong message each and every time. You can seem passive or weak when you're not, uncaring when you care a lot, stupid or vacant when you have a lot to say.
One of the biggest problems with all of my relationships has been this. I can't tell you how many times I've gotten into an argument with someone and it's ended with me standing there, silent, while the other person stands there shouting "Aren't you going to say anything?"
The problem is, I can't.