I've heard of a similar theory, but the one that I heard wasn't based around sexuality. Basically, the theory said that people will look for mates based on whatever their parents were. For example, if the father was a really good handyman, then their gay son or straight daughter will mostly likely prefer to date handymen. Same thing applies with parent-child relationships. If someone had an abusive parent, then they will most likely end up with an abusive partner.
By the way, the theory that you described isn't part of the "gay is a choice" argument. Trust me, those people don't usually bring up one's upbringing unless they want to rant about "those confounded liberals are letting their children to be gay again". Instead, they just bring up the "you choose your partners" and "you choose to present yourself as gay" (or at least come out of the closet) in order to back themselves up.
So don't worry about your post coming across as being pro-"gay = choice", because it's totally not.
EDIT: Forgot to add - I'm a trans man and bisexual. I do have a poor relationship with controlling parents, but I don't think that affected my identity or sexuality. Especially not sexuality, because I primarily like laidback feminine men and women, and my workaholic, masculine parents definitely don't fit either of those categories.
