Speech about working conditions is indeed protected. Nothing in the letter is about working conditions.
Sure sounds like a discussion about workplace policies and enforcement to me.
You can dislike something and also not think it's illegal.
Is that workplace conditions?
Also, oddly enough, "official company communications" is not workplace conditions. You do not have a legal right to discuss company communications!
There is an increasingly troublesome number of people entering the industry who simply don't enjoy working hard. I think every company would do better to fire them.
I take it you are in a country that doesn't support freedom and basic rights.