Why do gays believe that ex-gays are just lying to themselves?

i think its dispicable that some gays and s say that an ex-gay is trying to "deny himself and his innate desires by attempting to stop being gay." Someone said that to me once. But who are you all to say that im suppressing myself? People go through many changes, including attraction, and i should not be told to stop "denying myself" if i decide to change my actions. I don't agree with ex-gays trying to get others to change either. The bottom line is that people should have free will, without being told they are "sinners" or "are denying themselves." If someone wants to stop being gay, let them try it. They will figure out what they want, without a person getting enraged at "another gay afraid to be himself." Can I hear an arguement against this?