There we go, the "slippery slope" argument used by anyone who is desperate to back their point up without actually talking about the issue at hand. Good stuff, junior.
But sure, let's go along with your retarded assertion: what if Bob Costas looked right into the camera and yelled "Women should not have the right to vote!"...
Why should I be upset about his remarks, even though I disagree with him? He'd be fired and would never be able to work in broadcasting again (understandably so) but nothing about the situation would upset me. Again, the man is a football commentator, not the President. His views have no affect whatsoever on my life, or yours, or the voting rights of women, or gun control, or any other important issue for that matter.
I think it's odd that you're upset about a stranger voicing his opinion (in the wake of an emotionally-charged tragedy too). Considering the fact that one of the most highly-valued tenets of American society is freedom of speech, I think he and anyone else should be allowed to speak their mind. If they choose to do it in such a public setting while representing their employers, the consequences are on them, but they still have that right.
You mentioning the Constitution while arguing Costas should not have said what he said is pretty damn ironic when the very first amendment to the Constitution guarantees protection of a man's freedom of speech.