I used to think as nice, but not too important, but then I was in a relationship with someone I was sexually incompatible with. At first we both were "oh well. Not everyone matches on everything, right?" and we thought we'd make it work anyways.
But man, it's incredible how many other problems started coming up as a result. In the end there was pretty much nothing going right, and a lot of it had to do with the fact that we resented each other due to bedroom stuff.
So now I think sexual compatibility is pretty important.
Okay, so that wasn't exactly your question. I also think of sex as important to me, in my life (although not specifically intercourse) and the only reason why I think I could have a relationship with an asexual person is because I'm poly.
About other people's sexual experience, I don't really care. I don't care at all if they're not a partner, because that's not something that affects me one way or the other, and if they are a partner it only affects me insofar as I want to know if they've had no experiences at all or very few so I can be kind of a guide or something and make sure it's a great experience for them.
I think the virgin = loser thing is because people who troll you will try and find something that hurts, and a lot of people aren't virgin because they want to be, but because they have lacked the confidence or opportunity to have sex. In such cases, because they wish they weren't a virgin, reminded them and calling them a loser for it is hurtful because it's reflecting how they feel about themselves.
As far as people who say, for instance "people who save themselves are stupid", well I can't say I understand why you'd care if you're not dating one.
I'm pretty sex-positive myself so I don't understand the insults towards people who have sex often either. Sure you can see it as indulging a pleasure and think it's wrong, but you rarely see the same kind of attitude towards people who eat a lot of cake or play a lot of videogames ("a lot" being defined by "as often as the person who has a lot of sex has sex, and for as long").
I mean, you can hear someone being called a slut because they had a single one-night stand. While excess can be bad with pretty much everything, with sex the excess sometimes seems to start really, really early in some people's minds.