When you start thinking about which MLB teams' fanbases have the filthiest mouths, there's a good chance a few cities instantly jump to mind.In fact, there's a good chance Philadelphia popped into your head. It did for me.But a new survey from Vegas Insider has found the most foul-mouthed fanbases in the MLB, and the top team might surprise you a little at first... and then it will make total sense.That team? Technically, a franchise that played in Philadelphia at one point, but is now in Sacramento limbonow in Sacramento limbo ahead of a move to Vegas: the Athletics.PHILLIES PLAYERS SCATTER AS RAT RUNS ALONG DUGOUT DURING ANOTHER LOSS, EXTENDING SEVEN-GAME SKIDThis was determined by combing through each of the 30 Big League teams' subreddits on social media platform Reddit and determining the percentage of comments that contained an expletive.The A's led the league with a 6.03% of comments containing a swear word, the most common of which was "f--k."Second was the BostonBoston Red Sox — another one of my guesses for top dog — whose comments featured a four-letter word 5.114% of the time.PADRES PLAYERS HELD BACK AFTER CONFRONTING UMPIRES FOLLOWING CONTROVERSIAL SEASON-ENDING LOSS TO CUBSThe most swear-heavy team that made "s--t" their favorite word was the Houston Astros, who came in at No. 9.Now, I was a little surprised about the A's at first, but given the frustrating lack of success followed by their move out of Oakland, I get it.If my team were picking up shop, skipping town, and then playing in a minor league park for a few years, I'd probably let some expletives fly, too.ZERO BS. JUST DAKICH. TAKE THE DON'T @ ME PODCAST ON THE ROAD. DOWNLOAD NOW!The same study also measured the tone of comments, with the Boston Red Sox having the most negative fans, followed by the Athletics.Again. Somewhat self-explanatory.Hopefully, better days are ahead for the Athletics faithful.Otherwise, it seems like they may start adding some swear jars around the stadium.