First off, I believe Obama was born in Hawaii. Get that out of the way.
No possible reading of the law results in Cruz being anything other than a born citizen, even if born in Canada.
If Obama had been born outside the U.S., the law as written would result in him NOT being a born citizen.
Snopes covers it, and comes down firmly in the "Born in Hawaii" camp, but also covers the details about if 'not' born in the U.S. before calling them "moot".
It boils down to this:
If you are born to a U.S. citizen parent and non-U.S. citizen parent, outside the U.S., ==sometimes==, ==depending on some residency and age details== you will not be a born citizen.
Given that one of Obama's books openly claimed he was not born in the U.S. (The publisher's leaf, not Obama's text...), asking the question was legit. Smearing the question is NOT legit. However, refusing to let go of the question is also not legit, and that can be smeared as stupid, even if the question itself IS legit, and the demand for an answer was entirely legit.
Being an Obama birther at this point is stupid.
Questioning the legitimacy of demanding an answer from Obama is even more stupid.
Assuming this opens an issue for any office seeker born outside the U.S. is even more stupid still...