I think that's going a bit far JohnRambo, nobody has established here whether it does or doesn't damage anything. It's way overboard and wildly extrapolating to say that it would damage long-term bowel movements. Eating badly is what will damage your bowels, I hugely doubt anal sex would do anything at all about that.
I think that as a moderator of the forum, your word has a bit more weight on it than others. So maybe you could be a bit more cautious in what you say instead of scaring people away from anal.