I got a low ranked player which happened to actually play well which is great. If he didn't play well I'd boot him, but he didn't. Everytime I face champs there are gold or silver players in their team. The amount of assumptions made are just impressive.
It's only an issue if the gold/silver is pretending to be bad when they're actually really good. A team of 3 Champs and a Gold isn't breaking any rules if the Gold player is actually a gold player. Because when they matchmake, the Gold player will ultimately be a liability and need protection so they don't feed the enemy team kills. In your case, though, the lower ranked player had been pretending to be bad and when they were playing with you, started playing for real. And when you noticed this, you accepted it and continued to play with them despite the suspicious nature of a gold/silver player playing at your skill level. Other teams who also play several games with derankers also get banned, so it's not like this punishment is specific to you.
It doesn't help your case that immediately after that player got their qualifying rank, you and I FoundYoou were the very next people they played with, and you all remained as a team until ultimately getting banned. Also it doesn't help that they're on your XBL friend's list. Surprisingly, there was one game when the deranker was still qualifying where they actually matched with I FoundYoou
, and quit when it didn't look like they'd get a loss. I FoundYoou had no qualms playing with that player later after they'd ranked in Bronze, despite them quitting when they'd last teamed up, which seems odd for someone trying to legitimately rank up. It's also odd that a player ranked Bronze would suddenly match with you and I FoundYoou, who were Onyx and Diamond respectively at the time of your first match together in that group; even in Swat, that level of rank discrepancy is too large to allow for matching. The more likely scenario is that you formed a party after the deranker had finished qualifying and immediately went into Swat to take advantage of their low rank. It may even be the case that you knew this person beforehand and asked them to make a low ranked account with which you could use to benefit your account, since you are mutual XBL friends.
This is just what's available from public game records, and it's at the very least suspicious, even if it is only circumstantial evidence. The information the Enforcement team has access to is much more specific and detailed.