The only downside for this is some of the innocent users like replying/quoting or making report post will get affected. But if this can be enabled and disabled like if there are many reports that has the same contents, then it could be enabled to auto-delete once post with such keywords detected.
It wouldn't affect innocent users if restrictions were imposed on users below Jr. member rank for posting new topics with the filtered keyword. It shouldn't affect responses or replies from users in any section or even in that specific section.