I can have any opinion and nobody can do anything about it.
Indeed, you can
have an opinion, as can we all. It's when you
voice your opinion or put it into
writing that it becomes public. Be of no doubt - as soon as you write anything on the internet, it becomes public property. Pprune is not a private forum, it is a forum to which anyone can sign up to, as indeed are any number of other social and professional forums. Be very careful what you write - it might come back to bite you!