By the recent societal notions of bisexuality.
I hear far too often that bisexuals "can't make up their minds" about whether they like men or women, or that they "are just trying to convince people" that they're really mainly attracted to one gender with occasional "deviations".†
Bisexuality is a real and accepted expression of sexuality. It is not merely a phrase. There are people who are genuinely attracted to two genders in the world. The assertion otherwise is no better than the claims that homosexuality does not exist, or that gender-queerism does not exist. It is both incorrect and offensive.
Statistically, the rate of genuine bisexuals is relatively low compared to those who are "bisexual" due to fashion. This, too disturbs me, the notion of Fashionable Bisexuality. While I am open minded towards those of all lifestyles, I prefer honesty. Those who are straight or homosexual should not claim to be bisexual in my opinion. If one does have sexual escapades with both genders, but is in fact heterosexual or homosexual, I believe that they should simply admit this instead of lying about their sexuality.
Note: This article is my own opinion. I am open to criticism, as long as it is not flaming. I am also open to the fact that there will probably not be much feedback on this.
† Yes, all those quotation marks are justified. The terms used are verbatim from conversations and comment I have heard from various sources.