Depends... some of my friends have kids, in which case ponies are not only acceptable, they're a god damn saviour of mankind. They hypnotise small children and let the parents actually breath for once.
However a few friends of mine in their mid 20's watch it because they like it. For some reason. Which eludes me. I ask them why and they go 'cause it's AWESOME'. Erm. OK. Why is it awesome? The answer of 'because it is' when asked that question in this situation is hardly self explanitory. They've made comments that 'the animation is really good'. Well fine, I'd take that as an answer if you were in any way an artist or animator, but you're not.
I've seen the show plenty of times while its occupied small children and the thing is - it's VERY much a kids show. It's not like Shrek where it's full of subtle adult jokes the kids miss but we all laugh at. It's a CHILDRENS SHOW. Aimed at children. With stupidly obvious 'look this is the moral spelled out' sections at the end.
I'm a big believer in letting people do whatever the hell they want so long as it doesnt hurt anyone else, so if you want to watch a childrens show as a grown man/woman well good for you. But I do find it a little disturbing as I see no reason why someone would do so.
Porn... well porn is for adults. If I walked in on a mate watching porn then it would be awkward yes, but not disturbing. If they were just watching and not.. playing along.. then it wouldn't even be that awkward - I'd wander in and take the piss out of them, as friends do. It's a perfectly natural thing for adults to watch and we all know the reasons for it. So there's no reason for it to be disturbing.