Romney doesn't rebuttle every attack but at the same time, it's imporant that he rise above it. Does anyone remember Obama peeing his pants over Stanley McChrystal from a Rolling Stones magazine? His reaction made it look like he couldn't take any criticism. How about his near threatening behavior towards Jan Brewer a month ago over a book? If I didn't know any better, Obama would've had me thinking that no politicians had ever criticized each other. Sometimes reacting to every attack is worse than letting a few go.
Your point about choosing your battles is well taken, but I think this is one Romney should consider addressing- the Republicans have not been helped electorally by this whole debate about birth control. For him to say that a woman is in fact not a slut because she wants birth control as part of her health insurance policy might actually help with some of that swing vote he's supposed to be so great at getting. Especially when Santorum is on record saying Limbaugh went too far.