I’m somewhat reluctant to link to a profanity list here, but what the heck 
The list.txt file from this repo is probably a good starting point: GitHub - coffee-and-fun/google-profanity-words: Full list of bad words and top swear words banned by Google. · GitHub. It has 451 entries.
Note that depending on what types of discussions happen on your forum, you might not want to add all words from that list.