Translation:We have the freedom to express our opinions.
You are thinking of the word to which is analogous to the French Pour the Portuguese Para and the Norwegian å that is handled by the ~i at the end of esprimi. Some Esperantists like to see a por placed in places like that, for esthetic reasons, but it's not always vital that it be there.
Well, obviously one doesn't have to express one's opinion on every single thing. But in the words of Groucho Marx (I think), "The man who does not read is no better than the man who cannot read." I think this extends to every area of life – so, for instance, if one has the right to free speech but doesn't exercise it on the things that one believes really matters, I cannot think up a snappy ending to this sentence. But you know what I mean.