It states in the T&C which words are considered unacceptable. Obviously, use your best judgment if it doesn't specify otherwise.
I made an effort and googled "pain in the ass" +"homophobic slur" and I checked. To me the forum is like the Free Market, it's open and in your face to anyone reading so it's important to consider the wording. Also times change so it's good to keep up. Words like the n-word were normal words in Sweden (still in the north and the south) when I grew up, no one thought of it as condescending. We even had n-balls (chocolate-balls) and a ice cream named after the n-word. But as I said times change it's good to keep up. Google is your friend (mostly), idk about Bing though lol.