In my cheese's eaters country, this words imply that anyone can have / express any opinions, till their expression doesn't directly harm anyone else.
No one, in my country, could force anyone (muslims, jews, etc.) to read (and buy...) any newspaper.
Charlie has opinions and publishes them freely, it's a normal thing.
No one can decide which opinion anyone else should have, it's also a normal thing.
The murders are trying to force a prohibition on our society, on their sole purpose. They want impose which opinion should be allowed or not.
I'm surprised to see that this simple freedom principle isn't admitted in U.S.
I'll just buy the next Charlie's numero, even if i'm not on their ideological side. They can kill journalists, but the ideas and opinions can't be killed.