Specifically regarding its use to mean someone who is 'bent'? Someone who likes someone of the same-sex or is at least suspected of it? Does it include bisexuality? Is it polite or rude, subtle or overt? And when did you first start seeing this word?
not straight =
I first heard this word a few years ago. It is often used by younger people. It is a slang and should not be used in any formal situation. Like any slang, it can be rude or not depending on the context.
I do not believe it has any sexual reference though.
Yes, it's referring to homosexual recently.
It depends on the context. The word itself doesn't contain any offensive information.
It depends on the context, like CEO of Apple Cook admit he is bent in public media, may just state one truth, The word itself doesn't contain nay offensive information.
but if you are angry, and quarrel with someone, then you said the person is bent, then the guy will become crazy, it's really hurt.