I would assume that if a single person had not had sex by the time they were 35, (or was just plain committed to sexual purity regardless of their actual "status") then that was because they viewed sex and its place in life in the same way as I do, and I would be either glad of that (if I was interested in them) or otherwise just plain admiring of that (since we all still have hormones and it is not an easy road!).
I agree with 2Timothy2, a person's lack of experience with relationships does not automatically mean that there is something "wrong" with them, either - though it would mean that both people would need to communicate really openly, so in that sense it would be bound to affect the way they related if they were to date. I mean, say the girl had dated before and the guy hadn't - well the girl might have preconceived ideas about the "norms" in relationships - who calls and when, who pays, what "I am fine" means or whatever - and the person who had not dated would not have those preconceived ideas. Mind you, everyone is different, so having as few preconceived ideas as possible is always wise
It bugs me when people assume that there must be something "wrong" with someone who has either had no relationships or not had sex - as though it was for lack of opportunity or reflected badly on them or something, because 99.9% of the time, it is simply because of choices and priorities, and because people are doing what they feel they are called to do, and thus actually reflects positively on them. I know I know, I am a bit off topic, but I read an article the other day and it was referring to a single THIRTY YEAR OLD as a "spinster" - as IF! (And don't get me started on the media's double standards on that re men hehehe). I mean, my first thought was, heck when I turned 30 I remember thinking I was glad I wasn't married yet, any earlier would have been a mistake for me.
It's pretty deep in the psyche of western culture that "loved" and "accepted" = "married" by whatever age is the average in that culture. What a deception. And it is sadder when the church buys into it. I know it is driven by our God given desires and needs to be loved and accepted, but those are there so that we will find our home in Him - I know I am acceptable and loveable because He loves me, whether anyone else does or not - quite apart from the fact that romantic love is only one kind.
To get back on topic, anyone in the position described in the OP would have nothing but my respect. I would make no assumptions, and if I heard any negative comments about that person from anyone else, I would take them up on it.
Makk