Homosexuals already have the legal right to shout.
Certainly they do, and as you say, they shouting already. Their rights to express themselves are protected by the Constitution. But they do not want to allow the same rights for those who disagree with them.
Our Constitution grants people the freedom to practice their religion without federal intrusion. Most religions do not view homosexual relations as a legitimate basis for marriage. What is going on in Philadelphia right now is proof that the freedom of "sexual orientation" trumps religious beliefs. How is it possible that people quoting from the Bible get arrested for "ethnic intimidation?" How is it that telling someone they're "going to hell" (a place that legally does not exist) constitutes a threat? And what about people like myself, who regard marriage as a natural institution for one man and one woman in which to raise children, but do not base this view on religion?
I find it highly contradictory that certain groups advocate unconstitutional Hate Speech Laws, but then view an attempt to amend the constitution as political sacrilege.