Perfectly fine for them to do so, as long as it's clear that it's their own views. If the impression is given that the CoE takes this position, or endorses the standing of the position while against it then it's perfectly fine for them to take disciplinary action.
It's like everything, feel free to say what you want, but be ready for the backlash. Of course, the problem is that in our society the backlash for this, even if violent, would be irrelevant, the hold "strange" views, while the likes of Charlie Hebdo were intentionally provocative and offensive, and when they got severe backlash a big deal was made about it.