Then what makes you think other people can?

Because of their morals. Yes I believe in God. That's my main reasoning for it being "wrong" but if there is someone who doesn't believe in God, there really is no wrong or right. It's like our tastebuds in a way. They can change over time, so someone could be straight one day and then be gay the next. I have actually had a couple gay friends in the past. Even all of them told me it was a choice/preference. I remember one kid talking about girls one day a couple years ago then the next week he was talking about guys the same way.

You realize bisexuality is a thing, right? And a choice and a preference are not the same thing.