I agree, it's crap to attack Palin's parenting decisions. I'm sure she is a fine parent, and in life, stuff happens that is beyond your control "There but for the grace of God go we all," right? I also think that saying she is a bad mom for not being at home with her Down's Syndrome son Trig is utter poo. But perhaps those people weren't attacking her based on what they believed, but what they see as hypocrisy from the conservatives.
I think the thing that angers a lot of people is that many liberals wonder what makes it okay - by conservative standards ? It's fine with liberals to be a career mom, even with a special needs newborn, and it's fine to have a pregnant daughter that chooses to keep her baby. It is good and admirable to be able to balance being a mom and a successful careerwoman. But the camp from which Palin hails is the camp where her actions would NOT be considered okay. She is from the far-right wing of the Republican party, who are supposed to be all about "family values," about moms staying home and putting their careers on hold to be housewives. It's also the camp that, as you note, is all about abstinence and "virginity pledges" and is staunchly anti sex ed.
So here's the kicker - let's turn the situation around.
We can be sure, that not just lowly bloggers, but the conservative "big guns" from the Pat Robertsons and the Limbaughs and Hannitys on down, would be going bonkers with the news if Obama's daughters were teenagers and one of them were pregnant. The right wing talking heads would have a field day pointing to it and mocking the whole situation, claiming lack of family values, failure of sex education, and goodness knows what else.
I truly don't think most liberal bloggers - at least the sane ones - really believe that Palin is a bad mom. But what I think they do smell is the stench of double-speak (and double standards) in the rank and file of the conservatives.