There's a YouTube video where a guy tested the theory you guys are referring to.
Granted, it's one anecdote, but his findings were extremely persuasive.
If you genuinely don't fuck with people, it's seems likely that the matchmaking algorithm is going to do its best to pair you with players taking the same approach and if you are one of the guys that is just blastin' everyone, then you're going to get the same treatment.
He also stated that, in his experience, it only takes a couple of raids with out-of-character behavior to go from one grouping to the other.
I haven't taken a scientific approach, but my own experience(s) feel like they mirror this theory pretty well.