Why do single ladies get ostracized & harshly criticized for acting with actions & liberties of being single?

I posed a question here yesterday in regards to NSA relationships and having casual ; the feedback was, in retrospect, relatively informative and stimulating. However, there were a few ladies and gentlemen whom referenced by opinion of no-strings-attached as being in some respects, something of a harlot. But the thing is, I am a single independent lady and the I'm participating in is 100% safe (condoms and contraceptives are being put to good use)...why is it that single ladies are looked down upon for their private life by those whom aren't single? Why are we suddenly these horrible people because we have a more open life than those whom chose to be tied down? It's not that I don't have respect for my body, but I enjoy what goes on behind closed doors...I'm not spreading diseases, nor contracting them and I'm not increasing the population. Though I even made that clear in my prior question, I still received backlash regardless...why?