Reread what he said, because you're mischaracterizing it. He said that, in a situation where he had an opportunity to consciously size up his opponent and decide whether to deliver a blow that would injure him or not, he'd choose to try to break Brady's sternum.
When you don't have to injure someone to make the play, but you choose to deliberately try to inflict a serious injury anyway just for the hell of it, that's the definition of a cheap/dirty shot. Dunno how you can claim to be against those but have no problem with this.