@Brandon9000,
Actually he did say EVERYONE that is a Muslim would not be admitted into the country. His spokesman said he meant everyone that is a muslim.
He later clarified to say military members could come back then further clarified to say he wasn't referring to American citizens either. I guess if you want to argue that American citizens are not part of the group "everyone" then you might have an argument but that is a rather silly stance to take.
When applying for a visa to visit the US, the government can't ask the religion and ban certain religions without violating the US Constitution which states that no law respecting the practice of religion can be passed. It would also violate the equal protection clause.
Countries are not religions. Even you can understand that one. There is nothing in the Constitution banning laws respecting countries.
There is no guarantee of same sex marriage. There is a guarantee of equal protection. Being able to enter into a contract with certain adults but not others violates that equal protection. The government also offers benefits based on that contract of marriage which only allowing certain people to get those benefits while denying others without a valid government interest is the violation of the equal protection clause.