Oh, I assumed you were using a reasonable definition of clean online. You know, like "people who play to their best ability as if they were playing in front of a crowd at a premier event for a prize".
OK, sure. Let's assume a perfect world that doesn't exist, where you've got 100% clean and respectful players who never make mistakes, get greedy or just screw around to have fun. Let's assume that you've fixed matchmaking so that it always gives you perfect matches, and that your local player base is big enough to always give you your perfect match at any time of day and your netcode is so incredible that there is no negative effects from playing online.
Even given all that, there are still reasons to want to play with AI.