Anyway, I know someone from another forum who says that the f word that rhymeth with 'bag' does not mean much in America, and is a joke.

Do you think this is true?

That person would be wrong. It may be used by gay people the way there are African-Americans who use the N-word, but just like the N-word, that doesn't mean that anyone can use it indiscriminately.

It is a low-class word, just like the "N" word. Smart people use neither word. It avoids a lot of problems and hurt feelings.

I have to agree with the above posters. I struggle to think of a circumstance where it wouldn't be, at least, moderately offensive. I'm offended even when gay men use the word. However, it is less offensive than other variations.