First and foremost, both are dehumanizing and repugnant. Secondly, there is the 1st amendment to the Constitution of the United States.
For any who need refreshing on the 1st amendment:
Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
The establishment clause:
The first of the First Amendment's two religion clauses reads: “Congress shall make no law respecting an establishment of religion ... .” Note that the clause is absolute. It allows no law. It is also noteworthy that the clause forbids more than the establishment of religion by the government. It forbids even laws respecting an establishment of religion. The establishment clause sets up a line of demarcation between the functions and operations of the institutions of religion and government in our society. It does so because the framers of the First Amendment recognized that when the roles of the government and religion are intertwined, the result too often has been bloodshed or oppression.
http://www.firstamendmentcenter.org/rel_liberty/establishment/index.aspxIn the Court : Everson v. Board of Education
“The establishment of religion clause means at least this: Neither a state nor the federal government may set up a church. Neither can pass laws that aid one religion, aid all religions, or prefer one religion over another. Neither can force a person to go to or to remain away from church against his will or force him to profess a belief or disbelief in any religion... . Neither a state or the federal government may, openly or secretly, participate in the affairs of any religious organizations or groups and vice versa. In the words of Jefferson, the clause against establishment of religion by law was intended to erect 'a wall of separation between church and state.'"
It's time our political parties respect our laws and founding documents. Banning Gay marriage is a religious concept and/or interpretation of marriage. Establishing a separate law to pertain to the GLBT community is establishing a law to aid religion.