I agree with Dan Savage's comments up to a point. I think his observation about the paternalistic, classist justifications made by Gawker were very much on point.
I recall exactly when the GOP got really, really pissed at Hillary. It's when she didn't divorce Bill, even though it was pretty darn clear by that point that she couldn't possibly have not known who she married. No, she was shunned for not holding up their ideal of proper marriage. (which apparently demands divorce, in her particular case.)
However, both cases point out that the consequences for behavior that is actually bad and behavior that some interventionist fiddle-wit thinks is bad are the same, because they come from the same place and the same people. I shall be pointing to this as a good example when speaking of consequential ethics for years to come. It doesn't really matter if a private behavior is inherently harmful - if you can't arrange any way of making it safe to be "out" and do that thing - involving other people in "that thing" is particularly problematic.
Now, sometimes you just go and do it anyway - clearly, many millions do. But the people harmed that I'm concerned about are those who were involved without being consulted. One thing about a site like Ashley Madison - you can be pretty sure that there aren't many folks there against their will - so presumably they assessed the risks as well as they could. Whether this could be said of their partners and any children is quite another thing.