I think the ultimate arbitor of whether or not there is freedom of speech is whether or not there is anything to gain or lose by it, and this affects what rules are made and whether or not they're followed.
So, you might have a situation where technically it's forbidden but there's something to be gained by speaking out, even at risk, or at least privately with your peers, so you don't actually lose something (like your life or freedom). Or, it might be loudly proclaimed as a freedom but in practice not a good idea because of all the unspoken rules that would mean you lose status, credibility, popularity - and, at worst, people come to censor their own thoughts.
So really, to my mind, it's the unspoken rules that matter most and I'd much rather live in an environment of free thought, where I could at least be comfortable having dicverse opinions from my friends (whatever the laws on speech) than a place where I had to keep my thoughts to myself.