It sucks that you experienced whatever happened in the game. I'm pretty sure bungie has a reporting link you can send your proof to somewhere on the site, I'd say where but I've never done it. So I'll look and see if I can find it.
The only other thing is to report them on whatever console you play on.
Edit: Here's the link to the help post to report to Bungie's help email. Though I would imagine their network guys are probably quite busy with checking reports and looking over their code to tweak things.
https://www.bungie.net/mobi/en/about/Article?id=11929
WAIT! Found and example, and by a Ninja no less.
[url=http://halo.bungie.net/Forums/posts.aspx?postID=17820984&postRepeater1-p=1#17821184][/url]
Ahh the good old days before Bungie had its head up its ass and wasn't under Activision and the shit show that comes with that company.
And cue the ninjas with Bungie's "protect the cheater" policy and ban the whistle blower instead.
Bring back the Whambulence in the weekly updates Bungie. It'd solve alot of problems.
On the real, u probably gonna get banned but honestly I support what you do. Why shouldn't cheaters be exposed. Cheaters should get exposed by name and by video. The rules are whack. Out here protecting cheaters and shit.