I would suggest it is an involuntary act stemming from a sub-conscious response. Perhaps you could prevent this from occuring by reducing the emotional level of your mental response. In other words, try not to think of such acts as bad things, do not become so stressed about it, and possibly your body won't either.
You can't stop people from thinking you're trying to be manipulative. It's (teary eyes when mad) part of who you are for that to happen to you. And you can't help the natural reaction people may get from seeing it as well, it's hard wired into our systems.
Just expect it, and deal with it... It bothers you so much and you can't accept it (and peoples reactions) as being a unique part of you, then see a shrink or something to help try and see if there is anyway to help trick yourself into reacting another way.. and or taking anger management courses so you can manage your anger and in turn your tears.
i have the same problem...but then it turns to tears that are streaming down my face I get that angry .. I tried to explain something and it got me naggy so I started shouting causing tears which annoyed me even more...god its so annoying!