Hum, both shoplifting and grand theft are illegal. Adultery is not against the law, unless there's some kind of weird puritanical law in the US. So no, you can't equate the 2. At all. It's not like shoplifting to grand theft either. Your position on this matter if flawed. Adultery is a moral problem, you're equating it to a lawful problem.
I do not see the legal implications of either problem as particularly relevant, and only second to the moral side of it anyway. Normally I wouldn't see it this way, but in this case I do anyway because of the person who has been investigated. Like I have stated above, in most of the episodes of the show "To Catch a Predator", Chris Hansen primarily pointed out why it was morally wrong to do those things. The fact that it was against the law, came second.