Attacks on a mother and politician - it's not sexism

Since John McCain has picked the relatively unvetted Sarah Palin as his running mate. Attacks against her have escalated.
Some, even on the left, have balked at the criticisms leveled at Mrs. Palin that she cannot serve as vice president and be a good mother. These defenders of Palin as mother and politician argue that such statements amount to sexism.
The Gadfly would say otherwise. When I argue that Palin is not fit to be a politician and mother, not out of sexism, but based on Palin's track record.
I know several other women who are quite successful in work and as mothers, but Sarah Palin is not one of them.
Anyone looking at her record could see the failures as mother - her son may be a juvenile delinquent, forced to join to military to avoid jail time, her daughter is facing pregnancy at age 17.
Where was Mrs. Palin when her teenagers were romping around?
Also, Mrs. Palin delivers her youngest child, Trig, on a Friday and is back to work on a Monday?
Where is the motherly desire to take a few weeks off for maternity leave and take care of your child during his most fragile and critical days?
I won't even go into the issues of Mrs. Palin's record as a politician in Alaska, but suffice it to say that in and of itself should show how unqualified she is for national office.
The Gadfly argument here is that leadership should start in the home. That the problems Mrs. Palin's children are facing are a poor reflection of her abilities, or lack thereof, as a mother.
Men as well as women should be open to such criticism. It is not sexist to put forth such arguments, anymore than it is sexist to judge a woman based on her merit at work or home, rather than just her gender.