I am also pro choice and didn't have a problem with the ad running. I don't like censorship, which is what it would have been if the ad had been pulled. Those who are anti abortion take that belief seriously and have a right to be heard. Had CBS pulled the ad, it would not have been censorship. There's no such thing as censorship on private property. (Now, it might be breach of contract, but that's a different story
Tebow will definitely be in politics some day. I would bet any amount of money on that. You may be right