Personally (m), one reason I used to hate it was because it made me feel uncertain about my sexuality. I used to think something along the lines of am I really into guys, or do I just want to be into them for some reason?. But the biggest thing that bothered me was worrying I was being unauthentic with others. I already felt like I was being inauthentic (implicitly lying to since small degree) to straight people. Once I came out as bi, and I felt more strongly attracted to women for a day or two, I started feeling like I was lying to my gay friends, too.

It no longer bothers me. Probably because I've been in a relationship with a guy, or because I'm used to it, or because I just care less about what others would think about how I identify. Or maybe even because I've met more bi folks.