How do I stand up for the girl I'm dating?

[Jose]

This girl that I'm dating wasn't recently insulted on Twitter by an 11th grader (I'm a 10th grader) asking her if she was single yet. As in saying that shes always in relationships. He kept on adding to it and saying things that were disrespectful.
I want to stand up for her. It sounds easy but it's not. I'm 5'5, he's 5'9. Hes muscular but so am I. He's intimidating, I'm not. I'm just a nice guy and everybody know that. So not many people take me seriously. I'm small and I don't even curse. So my words aren't taken seriously either. I don't have a lot of guy friends either to back me up. I'm only the football team and that like my only strength I guess.
But I want to stand up for her so bad.
What do I do? I've never even been in a fight. He has. I don't really stand up for anybody. Including myself.
How do I stand up for her? Should I say something on Twitter? Do I wait 3 weeks until winter break over and say something to then? What do I do?

[Roses]

Even though it doesn't sound like it, this guy probably likes your girl friend. Why would he be bothering her, out of every other woman in your high school?
"Are you single yet?" (As in, all I'm doing is watching your status.)
Standing up for her? There's honestly no need to fight over this. I'd want my man to fight if a guy hit me, or grabbed my ass, or called me a bitch.
Something that deserves a nice punch in the jaw.
This is not a big deal. Take it as a compliment that your girl is probably on a lot of other guys' minds.
Just tell your girlfriend, "Babe, if someone ever hurts you, let me know."
Then, you can give him some choice words, as in, "Go mind your own fucking business, and leaver her alone. You can't have her, you never will have her, so move on with your shitty life." Something like that.

[postal p]

Just tell him to back off when you see him in school. If he hits you, he will get suspended.