You know, I know it's not for everyone, but really, as long as you douche exceedingly well, are not sucking a cock out of someone else's ass, is it really any worse than a nice deep rimjob? When i eat ass I am not just flicking the peripheral edge. No I am tonguing it, sucking on it, trying to fuck it with as much of my tongue as possible. I you can tell when you pass the involuntary sphincter; the feel of the smooth tissue of the anus. Do you think that bacteria are not there as well?
I don't know about you, but I can spend hours rimming. Literally. Now compare that to a minute, if that, of post anal suck time. Yes there is a risk, but honestly have never gotten so much as a stomach twinge from doing so.
And before you through out giardia, you would have already been infected with it if it was in your own anus. It is not a ever present organsim like e. choli. Yes I know that I could potentially get e. choli. Haven't had any symptoms in almost 3 years of doing this (not like it's an everyday occurrence, lol) From someone else's ass? Ummm...no. I do have limits. Knowing me i would want a parasitology report on them before hand.
And i know lot of people will disagree with me, and say "ewwww...how could you!" I do wonder though if any who inevetibly will are also ones who post on the adult website forums praising the activity and openly stating how hot it is and how they wish their partners would do it...
EDIT: forgot to answer the "why do I do I like doing it" part of the question. Well, he lies it , and that turns me on. I like feeling like i am doing something a teensy bit extreme. I get revved up doing it. And I wouldn't if he didn't kiss me after. That last part is important to me. Make me feel like a dirty slut, but please don't treat me like a two dollar whore.