Possibly the most common put-down of bisexuality, after "there's no such thing" or "it's not possible" is to be told that bisexuality is just a phase. It isn't, and this cliché is an especially insidious piece of biphobia.
When someone says "It's just a phase" they're not saying that bisexuality doesn't exist, or that people can't be bisexual. It may not sound aggressive - just bewildered, and so when many of us hear this we might relax and fall into a trap.
We might smile and say "not for me it isn't" or "for some people, sure, but not me".
That's a mistake - it sounds like a good comeback but it can actually support biphobia.
When you say "not for me it isn't", what you are doing is agreeing with the person saying "it's just a phase" and offering yourself as an exception. You are confirming that their generalisation is true, apart from you.
One suggested way to respond to "It's just a phase" has been to reply "well, so's life" or "being a teenager is just a phase too, but you can't say teenagers aren't real". But both of these are flawed as they are still agreeing that bisexuality is a phase - just one to be taken seriously. Or worse, a phase that (like being a teenager) you grow out of as you "mature".
Several other classic biphobic statements are "it's just a phase" in disguise:
None of these denies the existence of bisexuality, they're all just variants - bisexuality is seen as temporary and transitory.
Yes, some people who aren't bisexual sometimes identify as bisexual. Yes, those people may well later stop doing so.
But that doesn't mean that bisexuality cannot be a person's long-term sexuality. That doesn't mean the being bi stops when a person is in a long-term relationship.
Some people are attracted to only one sex, others to more than one. Why think that one of those circumstances can only be short term?
"Bisexuality? Oh, it's just a phase!"
"No - that's just a phrase!"