I want to tell my class that my friend is bi
Why do you want to out your friend? Are they not ready to say anything?
Yes, I find it offensive and I think my classmates should know
You should not talk about your friends sexuality in front of other people. She could be embarrassed or hurt that you would tell people with out permission.
I don't care. I think people should know about my friends sexuality.
Give her some time to tell people about it because that is something that is personal. She should be the one to bring it up when she is ready.