I agree with #87575. Although his post may sound offensive to some, we of all people should know never to be judgemental towards others.
I've never had anal sex, and I still have a fecal odor so I don't think anal sex is the cause but maybe it does make the odour worse? I do notice that right after I have a bowel movement if I don't take a shower after, then the odour is a lot more noticeable (even if I just took a shower before the bowel movement). So maybe there is something to what the op is saying.
Maybe if I did penetrate my anus with an object, it would make the odour worse? Who knows, but we shouldn't just dismiss someone's comments as weird or perverse even if it does offend us. Gay men and some straight women have anal sex, so why should we be offended by that?
And what the op is saying about other people reporting the same thing about the odour starting after having anal sex, why should we just dismiss that? He was saying they may have been infected with bad bacteria during the anal sex. Maybe its possible and other people who dont have anal sex have been infected by bad bacteria in other ways. Who knows, but any clues that may help determine a cause shouldn't just be dismissed.