Slander?

I recently commented and joined a group going against my school on face book. I discovered the hard way that it is called slander to express your oppinion (essentially). Freedom of speach is now illegal, I guess.

This a free country, am I right?
Swearing is NOT illegal, am I right?
Joining a facebook group is not illegal, am I right?
Then how the hell do they figure that any thing I said was ilegal. The group name was against the school, NOT anyone personally! And even if it was against the law (which aparently it is) who reports a face book group to the police?

I will quit ranting, now.

Thanks for reading. If you are interested in some cooking tips read my next post:) Thanks