There's an extra layer of shame to being told you're an old slut. A young woman's "sluttiness" can be excused in part because she hasn't lived long enough to buy into social mores, and she's too hormonal to delay gratification. But an older woman who admits that she likes erotic pleasure without all the packaging? That's not just slutty, apparently, it's freakish.
There will be many more dating opportunities and simply being rejected by one young woman does not imply that there is something wrong with you. There are a myriad of reasons why this young woman said that you are too decent for her that do not support the theory that girls just simply do not like you.