I don't see why Rubio would refuse to answer. At this point I think that people are recognizing that it is something that many people try during their college years and that the question at this point is basically who has not done it.
I actually thought his reasoning for not answering it was pretty good if he genuinely opposes it. There's no doubt he smoked it, but his point of younger people taking it as an example made plenty of sense. It's like that old Einstein failed math myth, where kids like to bring him up as an excuse for why failing a class is okay, when it isn't.
