Sure I can come out with non-religious beliefs about why it's different.
The differences are plain to see for anyone with common sense.
But what I find most ignorant is how people automatically dismiss religious morals as being bad and worthless or unjustifiable.
How about those non-judgemental unbiased open minds you claim to have ?
Marriage has had a set precedent for over a hundred years.
Now the gays want to change the definition of marriage.
You claim that the heteros want to change things.
No.
They only want their institution and precedent "to be left alone".
It's different.
CIVIL UNIONS WITH EQUAL RIGHTS=yes
Marriage=no, that precedent has already been established