As the definitions of not only gender roles and sexuality, but gender assignment shift, sexual attraction is constantly under fire. Some people say that you just love who you love. That may be a different sex from one relationship to another. Is that changing sexuality? A man may prefer blondes but end up finding love with a brunette. Isn't this the same thing? Love should not be tethered to one thing or another. That defeats the purpose. By defining who we can or cannot love, we might as well return to arranged marriages and sex only for procreation.
No, I do not think that people can change which sex they are attracted to, because I feel like people are born either straight or gay, and you can not change this in any way. You can try and fake it, but you will still actually like one sex or the other.
I personally think that people are born the way they were born either a female or a male. I personally think that people cannot change their sexual orientation because male that is trying to be a female would not get pregnant no matter how hard they change themselves from the outside as well as a female trying to be a male the female would still have periods.
It is eminently clear from the failure of camps designed to 'cure' homosexuality that humans are able to choose or decide to change their sexuality. However, it must be acknowledged that sexual orientation is mutable: not able to be consciously changed, but subject to shifts over time. The idea of a set-in-stone sexuality is inconsistent with the mutability of human personality.
No one has ever changed their orientation from straight to gay or from gay to straight. They are either lying for publicity, money, acceptance from family or community or some other reason. They might have been bisexual and it took them a long time to come to terms with one part of their attraction. Reparative therapy does not work and it is very mentally damaging.