Can somebody explain to me the gay marriage issue please from a legal perspective?

In the states which ban gay marriage constitutionally but legalizes it through civil unions, it is merely a matter of terminology. The gays, which tend to see government as a god, seek its validation and want it to be called marriage. The right wing religious nuts, which hate gays more than Satan, do not want to share the same title with gays. Both sides are idiots since ALL marriages are basically civil unions. Marriage is a religious term and therefore has no bearing on the state. The state is trying to appease both sides.

from a legal perspective the states are infringing on peoples 14th amendment rights as they are not getting their equal protection under the law. This will eventually go to the supreme court where the court will rule that states cant deny any specific group their right to marriage. The 14th amendment is by far the most important amendment when it comes to civil rights cases. It is what almost every landmark case has been based around. States have the power to control marriage, but can not treat one group differently then another group as that is a violation of the constitution.

In Nevada, the state has two separate forms---one for straights, one for gays. Both have the same legal protections, just different terms. One is marriage, the other is civil union. Since the state cannot tell religions who they can and cannot marry, then, yes, an Elvis impersonator can marry a same-sex couple--as long as they fill out the appropriate civil union form either after or before the ceremony, just like in any marriage ceremony. My uncle and his partner were legally "civil unioned" in Vegas by a man dressed as Liza Minelli.

From a legal perspective. The Government needs to get out of religion. The States can do as they want in this issue. It should never go before any court. The law states that the Government can not involve themselves in religion. No matter the disputes. They are to be handled by the churches themselves.

Work benefit insurance companies don't want to extend benefits to gay partners. That's the long and short of it.

It gets even more complicated than you pointed out. In New Mexico, for example, you can have two gay couples living in neighboring houses, one couple is legally recognized by the state while they other couple not. How can that be? Well, New Mexico is one of three states that will recognize gay marriage or civil unions in other states, although they have no such laws themselves. So if one couple marries in Vegas, NM will recognize it back home. The other couple cannot get married in NM and be recognized. It's odd.