How to report a youtube user for cheating?

There's a YouTube user who entitles himself "Silver - Minecraft Beast" at the link http://www.youtube.com/...ythroughs/

I believe this user is cheating because he inexplicably gains several dozens of subscribers during a finite amount of time, then keeps at the same level for up to 30 hours at a time, then ends up gaining several dozen more subscribers.
Relating to that, and another reason why he may be boosting his subscribers is his subscriber count is going up at a rate faster than his viewership rate. This can be explained by having him messaging a user and asking to subscribe, but hundreds and only at certain times gaining subscribers is not correct.

How do I report this guy for cheating?

He might be SubBotting. It's hard to explain though, you could contact YouTube and report him for gaining so many Subs instantly.