You keep pointing to David's sins, attempting to use those sins to justify Michal's sin. The point is, 2 wrongs do not make a right.
Your question was "Why do we judge Michal so harshly?", and I don't think I do. I have "judged" that Michal was sinning in the way that she felt toward David. That's all.
I can understand the reasons Michal felt as she did toward David, but it does not
justify those feelings.
But let's take a look at this statement;
Your repeated use of the term "Clintonesque" and stating that David was "cavorting half-naked before young women" implies that his purpose was to impress those young women. But that's not what scripture says. It says;
2 Samuel 6:21-22 (NIV)
David said to Michal, "It was before the LORD, who chose me rather than your father or anyone from his house when he appointed me ruler over the LORD's people IsraelI will celebrate before the LORD. I will become even more undignified than this, and I will be humiliated in my own eyes. But by these slave girls you spoke of, I will be held in honor."
What this is telling us is that while Michal apparently held the same assumption

as you that David was simply showing off for the ladies, he was in actuality dancing before the Lord. That is, unless you believe that David was lying, and really did just want to show off for the ladies, which I think would be a huge assumption

.