Frankly I think many who leave do get involved in practices forbidden by the religion. Things that are "immoral" to JW's, but likely not so to the "average Joe". Recreational marijuana is becoming acceptable in many US States. Grossly immoral to a devout JW. My 65 year old fabulously successful conservative (rabid republican) attorney friend asks me recently if I am "420 friendly".(No. Not that it's "immoral". Just not my drug of choice.)
Any kind of sex (even masturbation and especially anal or oral sex) by single JW's is "immoral", whereas "normal", healthy, single adults are going to have sex (if they can arrange to do so). JW's who leave that have suppressed same-sex attraction for years are going to at least experiment with it. Many "normal" youths (especially girls) have done that by High School and may have even tried threesomes.
So, yes.......all those self-righteous JW's look down with disdain at all those who have left the flock to pursue their "immoral" desires. Desires and actions that are probably just "normal" things to all their "new" friends and associates.