...Is it possible that a gay person does not understand what it means to be bisexual?
Believe it or not - Yes! (not necessarily Dreu personally!)
This is where the problems arise. Many gay people think its as straightforward as sleeping with both sexes - getting the best of both worlds, being greedy, in denial etc. - which it isn't.
Some people identify as bisexual because they're physically attracted to male and female. Others because they are physically attracted to males, but also need a strong emotional relationship to females. For some it's the other way round, and for others it's varying degrees of all of the above!
I could label myself as bisexual I suppose in that whilst I only sleep with men, I've always had to have an extremely strong emotional 'relationship' with a woman. One of my friends refers to me as his 'soulmate' and labels himself as bisexual because he loves me - on an emotional level - as much as his wife. Even his wife acknowledges this.
However, many of our views on different races, cultures, religions, sexuality, countries are 'fed' to us. We think of India and the Taj Mahal appears. Ethiopia, we think of famine. Paris we think of the Eiffel Tower - that is, until we go there ourselves and suddenly we have firsthand experience and a new memory that comes to mind when those places are discussed.
So, many gay people perceive bisexuals as in denial, greedy, arrogant, etc and many bisexuals perceive gay people to be less than men, effeminate, etc.
We should all of us be saying, 'Give me a different experience, so that I have my own memory the next time it's discussed'.