Those scientists do something called "research" which requires them to not only talk to people who are homosexual but to actually listen to what they say. They then use this data to prove, or disprove, their theories.
So, no, they're not blinkered because they approach this with an open mind and they use facts (rather than prejudice or "God says...") to influence their thinking. In general, anyway; some scientists are crap. Those nutjobs who distort paleontological evidence to try to prove "intelligent design", for instance, do very bad science.
So how did you reach your conclusion that homosexuality is a choice?