Muscles don't care for altruism or the environment. A Goblin can attain the same level of bodily mastery by punching a lot just like anyone else. All cultures have some level of fighting, and especially considering in the Goblin Slums of Kezan where everyone has to fight sometimes tooth and nail for every copper and often fight off goons who beat up and rough-house to enforce debt-collection it would be in a Goblin's best interest to try and learn some self-defense if not for themselves but also to maybe protect their assets and investments or clientele. When Bruisers come knocking, you gotta protect what's yours. Even if it means punching a few mooks - and everyone can punch and kick. It's not like Goblins can't be good people - they just like making money. Being good at punching, and making money while doing it? Well, that works out just fine. Now, I'm not saying there are underground fighting rings where Goblins bet a lot of money on who beats up who, but I also wouldn't be surprised at all to see it. And if we're strictly talking about the Pandaren type of monks, it's not like Goblins don't like brew - they show up every Brewfest and have a lot of history there, so mastering the drunken fist wouldn't be out of the question either. And it's not like Goblins won't get religious when it's in their best interests - Goblins sell faithful healing in businesses like the Airborne Priests, and I'm sure some Goblin can figure out how to sell medicinal herbal teas and acupuncture if not booze or even just a raw fist. There's a lot of profit to be had in learning to make your body a weapon - Gnomes have figured it out, Vulpera have figured it out, heck everyone else is making money on it. Chen Stormstout didn't just inherit a family fortune - it's a family business. And Goblins love business.