Prudent in the sense that Kathryn apparently felt justified in criticizing the people who spoke in opposition to the campaign before the ad aired.
As I cannot speak for Kathryn, I could only answer this from my perception of the alleged events. If and a big If mind you, Kathryn did criticise other posters (justified or not) in the end what Kathryn was saying was absolutely correct. And, it was those who criticised what Kathryn was saying who ended up being less than correct in this matter.
Would I say it was prudent of Kathryn?
1) For the sake of honesty and truth, I would have to say yes.
2) For the sake of being attacked for being right, and the posters who cannot accept that Kathryn was right and therefore cannot let the subject drop until they twist it around far enough to gain some sort of personal mental victory from it. As in your own personal attacks on Kathryn (see this post I am replying to), that I would say would have to be up to Kathryn to decide. Being right, doesn't always win you popularity contests and can also make you the target of ridicule.
Answer me this, then: the OP referred to the ad as "pro-life". I've seen the ad (one of them, anyway - anyone have a link to the second one?); there's nothing in it that explicitly refers to the "pro-life" movement. Where did this interpretation come from?
You are asking me questions I have no answer for, unless I take a wild guess which makes the question unreasonable. What I can say without guessing an answer, is it came from association patterns stored in peoples heads, whether they were for or against the ad. Depending on whether they related to this ad being positive or negative in context.
From a marketing perspective, an add could show peanuts being poured into a bag, and that is all that the ad showed, they could relate and associate this ad, to buying a new car. It is not what the ad shows which counts, it is how the ad is related and associated to. I will not go into detail of the hows and whys of advertising, except to say, those against the ad, were their own worst enemy.