Same-sex leaning: By birth for some, by choice for others

Would-be Presidential candidate Ben Carson keeps proving over and over that he is not ready for prime time.  You may have heard his opinion this week that being gay is "absolutely" a matter of choice---as evidenced, he says, by the homosexuality displayed in prisons by inmates.  Is he looney? Or is he correct?  Or is he partly looney and partly correct? Okay, here is where I come down on that:

As a never-been-married total layperson on such matters, but a fairly seasoned people-watcher, I believe it would be incorrect to pretend it is a one-size-fits-all proposition.  The gays and lesbians I have known over the years seem to me to fit, more or less, into one of about 3 main categories:  (1) Those who are born with a biological makeup, perhaps genetic or hormonal, that gives them a propensity for same-sex attraction; (2) Those to whom it is a personal preference, like preferring someone older, or younger, or bigger, or skinnier, or lighter, or darker, etc.; and (3) Those hipsters who gear their dating life around what is trendy at the time, especially within their own circle of peers.

Bottom line?  I would surmise that most of the time you are born with it, but sometimes you choose it.  Either way is okay by me. It's none of my business.  That is, until you get into trying to redefine marriage, an institution which human civilization invented a long time ago more as a way to create a stable home situation for having and raising children than to create a nice bond between people who love one another or to provide them with legal rights.

In the olden days, when church and state were inextricably linked, 'marriage' worked for all of the above.  But, now that times have changed, there needs to be an entirely new civil institution just for the 'bonding' and 'legal rights' issues, split off entirely from the largely religious institution of 'marriage'.

To arbitrarily give 'marriage' a broader meaning than it has always had would serve to completely water down the significance of every marriage that has ever taken place.  Suddenly, whatever our grandparents and all those other generations of kinfolk had that was subsequently passed down to us as 'family' would be rendered a whole lot less meaningful.  How can that possibly be right?