Why would I be for the Supreme Court ruling but against gay marriage

I join millions of Americans in celebrating what I believe is a just ruling that finally affirms that gay marriage is just as legitimate as straight marriage in our country.  For far too long they have been treated as second class citizens in that straights have been afforded dozens of benefits that gay couples were denied.
As a Christian my personal belief is that homosexuality is a sin. But the federal government government is passing judgment on my or anyone else's personal beliefs.  They can't.  It is actually protected. It would also be impossible to define marriage based on a religious belief as there are dozens of religions who have lots of different opinions on what makes a marriage.
I have thoughtfor years that CS Lewis was correct when he stated in his radio address to Britain during WWII that the word marriage is a government institution.  Christians who want to hold themselves to the Biblical standard should first make sure they know what that standard is and then have a 2nd word for it. Marriage from a Biblical point of view has little in common with what most Americans call marriage.
Like all standards set in the Bible it is humanly impossible to meet. They are only possible with the Holy Spirit living inside you. And that is impossible without Jesus. As Christ said when asked about the possibility of the rich man entering heaven.  "It would be easier to thread the eye of a needle with a camel. But with God all things are possible".  May God richly bless you in this life and the next.