I was not suggesting that. But dating is one of the few instances where "judging" to an extent is necessary. It's risk assesment, combined with pattern recognition. In relationships, we're always faced with incomplete information. It's impossible to learn everything essential about another person, even if they're an open book. The question is not "Will everyone who's had sex before marriage be unfaithful?" That's a rhetorical, straw-man argument-phrased-as-a-question. The answer is, of course, "no". More likely? I'd say "yes".
The real question is "Given this person's past experience (according to the information I have), what is the probability I could expect certain behaviors in the future? If these behaviors show up in our future relationship, would that relationship still provide the security and emotional connection I require? To what extent? Is this acceptable risk?" As I gained more (albiet limited) experience, my answers changed drastically.
There are also major differences between the WoW and sex. Sex is biologically essential for the survival of the species, and our bodies have been hardwired to recognize that. There are exceptions, but I would readily say that the Law of Chasisty is a more common problem than the WoW.