Yes and No. As with everything, it's complicated.
It certainly can be disrespectful, and yes, that is part of the turn on. As a bi male switch I've been on both ends of it (and yes, I love it, and no I don't even entirely understand why). I mean, clean or not, this thing was just in your ass! Now it's going into your mouth? Damn...
Of course, there always has to be consent, either direct consent at the moment if it's a newer partner or consent given prior conversation or some other way if establishing they are OK with it. In most cases of sexual consent it would be a turn off to suddenly stop and ask for consent directly in the moment, but this could be the one case where it's a turn on (if they unexpectedly say yes, anyway... asking and getting a no could derail the whole experience though I did have one woman quickly say "no" and promptly squeezed her ass on my cock and push back into me to keep the moment going and it worked... And later let me do it in another session lol)
Doesn't necessarily mean you don't respect your partner as a person, but to have that passionate moment where they are allowing you to disrespect them, violate them in a way you know most "normal" people won't.
Being on the receiving end, it's showing your willingness to do something like this for your partner, in an act of submission to them. Letting them take it to a certain extreme and being a willing "victim" is the turn on for me.
Probably the time that turned me on the most was when I had a partner for years and she had made it very, very, clear she would NEVER do ass to mouth and I respected that, and for years never even asked. Then one day I was fucking her in the ass and she stops and says "pulls it out stick it in my mouth, I know you want to" and OMG... That sudden turn just... Well... Knowing how she felt and yet not just being willing but almost insisting I do it that night... Mind fuck complete... I exploded in her mouth.
Don't know if this answers the question, but figured I'd offer my perspective. I have more thoughts on it but don't want to ramble...