Request for Serious Debate

The US seems to have lost all capability to debate when it comes to serious issues. Generally it turns into a shouting match lead by the loudest ignorant person around. For instance the Tea-bagger-or-bags-or-whatever-they-wish-to-be-called seem to never run out of steam. They are against "Czars" though this term was started by a republican and has never been questioned under any other presidents. Or what about health care being used as a way to compare Obama to Hitler (ironically this is a slap in the face to anyone who fought Nazism).

Today I ask for a serious debate about Homosexuality on two fronts: Marriage and the Military. Lets get things started: the military has the famous don´t ask don´t tell policy that is used to prohibit homosexuals from serving openly. The reason given is usually something about unit cohesion though no proof is ever presented to back up this claim. Is this the best answer for the reason that gays are discriminated against? Because straight people are uncomfortable, though no one has been able to prove this? Every other western democracy allows homosexuals to serve openly and their militaries aren´t falling into disarray and confusion or turning to orgies either. Please give me a good reason beyond some form of conservative religious morality.

Secondly we arrive at marriage. Marriage is a state institution. What that means is that in terms of legal framework it is something that the state recognizes as a union of two individuals (it can be talked of in more romantic terms but that is not the purpose of this post). At this point in time the US states tend to recognize only the marriage between a man and a woman (defined by what and shouldn´t they have some athletic gender test to make sure that this is always followed). What is the reason for denying marriage to same sex couples who wish to look out for one another until they die in both the romantic sense as well as the legal (financial and death) sense? Is there any reason beyond conservative religious morality that is used to defend straight marriage as being the only option that should be tolerated?

For those who wish to cling to religious answers please note your constitution is secular and calls for a separation of church and state so as not to discriminate against minority groups and others who do not share the same religion.