facts-about-bisexuality:

Fact: It’s not true that “everyone is a little bi.” There are lots of lesbian and gay people out there who have fought hard to understand their identity, and they know for a fact they’re not bi. 

Plus, society certainly doesn’t treat bisexual people like we are the norm. The fact that we are treated differently matters, and saying that “everyone is a little bi” delegitimizes our experiences of oppression, our journeys to self-discovery, and our sense of community and identity.