I actually wasn't, if only because I'd watched so much. He used to be on a show called GameGrumps and Aren, the other host, would occasionally make fun of him for being racist. I more or less blew it off then, but it does help explain his disappearance from the show, explained in a spoiler if you care.
Basically the show was pretty successful and they were adding another show on put on by 2 friends of theirs, Ross and Danny. At one point Danny was suddenly in GameGrumps and all the series that Jon and Aren were doing were abruptly cut off. My guess since this thing is that Aren saw that GG was getting big, and he was like "Yeah, Jon's eventually going to fuck it up so he better be cut out before it happens." He did cameo in a Jontron episode since then, though.
This is pretty much baseless speculation on my part though, but it makes sense to me.