Is there Something Wrong?

I have a question. It might seem silly to you, but it's something that's been bothering me lately.
Is being bisexual wrong?
I ask this because I get alot of people that act as if liking guys AND girls is wrong. I don't get it. Gay/lesbian people want to be accepted, but alot of gay/lesbian people don't except bisexuals.
Why is that?
Is it becasue bisexuals like both sexes and it's like a betrayal, or do is it that you dont think it's fair that I like both and you don't. I certainly don't get it.
Straight people don't get it. They think that because you like the opposite sex that you should just mask the feelings for the same sex.
Now I know this isn't pointed at ALL gay/lesbian, and straight people. Just the few that I've encountered but is liking both sexes wrong to you?
Is there something wrong?
I don't understand why someone might feel that way but I'd really like to know why others MIGHT feel like that.
That's it for now......