This is not true. I can call myself a doctor a lawyer or a cop or anything like that and it is protected speech so long as I am not attempting to perform the professional duties of that job.
It's free speech.
It's not up to the board of engineers to arbitrarily decide what isn't isn't the professional duties of a job and then punish people who say things they don't like. It's statutorily defined and this activity was not.
The courts made the entirely wrong decision which is very normal for the US.