I mean, just look at marriage from a secular standpoint (THE DEMONS ARE GONNA GET YOU)
It’s essentially a contract stating your desire to cohabit with another person, and, if it happens to be a male/female relationship, you’ll probably end up having kids. From a purely legal standpoint, marriage carries no special spiritual or magical connotation, so to say that it MUST be restricted to one facet of humanity is completely ridiculous.
Not a straight, white male? I’m sorry, but we can’t lease you a Honda today. Yes, I know it’s just a legal contract, but leasing a car is viewed as a very high honor in many cultures, and the idea of you driving around a hybrid subcompact when you don’t believe in the God of Abraham is simply appalling.