This would all be cleared up real quick if someone just asked about it on that Xbox forum.
Except they only share that info with the account holder. They've cracked way down on posting information related to bans publicly, probably for legal reasons.
I don't believe the original poster is guilty, but I also will not assume Microsoft was wrong either (I've read way too many posts on the support forum about how someone was innocent when it was obvious that they tampered with their HDD). Since there will never be enough information revealed it's really hard to make any kind of judgement call.
Sucks the guy got banned though. Trying to navigate their customer service for anything is kind of a pain in the ass. At least it was years ago, I don't know i that's changed at all over time.