I'd suggest you actually go through with it and lay down your argument in full.
OK:
[violence} doesn't achieve anything.
Yes it does. For example if you beat someone up you can take their stuff. Or thwart their political designs. If you beat up enough people well enough you can execute social change. In fact the vast majority of positive social change (and even more negative social change) that has occurred in the history of mankind has relied on violence.
Violence is the crudest form of power we have. Power does stuff. Pretending violence doesn't achieve anything is gross self delusion.
Don't let your pacifist politics corrupt your very model of reality. Instead, understand what violence does and does not achieve and then act on your preference for non-violence.
Ah, well, yes, violence will get you what you want in the short term, but unless you exterminate your enemies, they'll still be a liability: violence doesn't convince anyone, it just makes them more tractable. Heck, even verbal combat, that is, argument, doesn't usually serve any purpose but convince both parties that they are right.
So, yes, "violence (and rudeness, for that matter) achieves nothing" is a gross simplification. "Violence brings very flawed achievements and has lots of terrible drawbacks" would be much more accurate.
I have found this most wonderful (if fairly lengthy) article, and thought you would enjoy having it brought to your attention.
It is so good, I think we should include it among the references in the "Politics is the Mind Killer" wiki page. But, before that, I submit it to you, and ask you: is there anything in this article that would warrant its exclusion from this site? I mean, besides the fact that it is about politics, and written by a notorious Social-democrat (And is that in itself grounds for exclusion?).