There's nothing to justify. It you have a relationship or sex with anyone, you did that, it's a choice you made. Nobody is arguing that choice wasn't made.
What people are attempting to do is say that those choices somehow don't establish your sexuality, which is absolutely ridiculous on the level of saying committing a crime doesn't establish a person as a criminal.
I don't believe that sexuality is a choice because it is based on attraction that you can't control.
So you're saying that your choices being based upon attraction that you can't control somehow means they aren't a choice? That you are a robot and cannot choose based upon anything other than attraction? That you have absolutely no control over your own thoughts and feelings?
As a basic rule, please imagine that all of my posts contain the following: generality only, just for the sake of argument.
So you do things "for the sake of argument", then. I thought that's what you accused me of doing and called me a "troll". Seems we now know who the real troll is (hint: it's you).