Pirkei Avot, chapter 2, paragraph 1: "Rabbi (Yehuda HaNasi) said . . . 'Be as scrupulous in performing a "minor" mitzvah as in a "major" mitzvah, for you do not know the reward given for the respective mitzvot.'"
Some segments of the Orthodox community seem to have the same attitude toward sin, not differentiating between minor infractions of halachah (Jewish religious law) and serious, even life-altering, violations thereof. ADDeRabbi has complained about this both in the past and more recently, and has strongly recommended that a "hierarchy of violations" be recognized, acknowledging the fact that some sins are, in fact, much worse than others.
Here's the heart of his post on the misbehavior in Monticello:
"I’m not sure if I should laugh or cry at the equation between immodest dress and drug use. I have been taught that in order to be a good Jew, one must first be a good human being. Being Jewish does not absolve one from being a mensch. All of the behaviors discussed are symptomatic of the ‘at-risk’ youth. And I ask: at risk of what? Becoming Modern Orthodox? Intermarrying? Dying of a drug overdose? Contracting STDs? I think that a hierarchy of ‘risks’ must be catalogued, and fast, lest mountains be turned into molehills and vice versa (like in the old ‘it leads to mixed dancing’ joke)."As I commented there, "I have a serious problem with the automatic assumption, in some segments of the Orthodox community, that there's no such thing as innocent, wholesome activities that involve both males and females in the same place at the same time. Seriously, how intimate can one get with a bowling ball in hand or a mouth full of pizza?"
I read somewhere (given my lack of a decent Jewish education, it was probably on a blog) that the rabbis have said, "If you forbid that which is permitted, people will do that which is forbidden." See here for proof, should you happen to need any.
The Hillel (standing-on-one-foot) version: If you forbid everything, then people will do anything, on the assumption that, as long as they already have the (bad) name, they might as well play the "game" (do that of which they've been accused anyway). If you're going to call me a whore or a womanizer just for talking to a person of the opposite sex in a pizza parlor, I might just as well have sex. After all, what difference does it make in your eyes, anyway?
Bottom line: If males and females have no opportunities to be together under reputable circumstances, they'll seek disreputable ones.