The thing is, I'm okay with this comms person saying that just generically posting "kys" is bad and maybe even actually abusive to employees as they say, but they aren't giving detractors a way of attacking management, just saying that the existing ways are all wrong, which is equivalent to them posing themselves as a human shield and saying "You can't attack management, you'll just be hitting me, and I'm just a worker. You wouldn't attack a worker would you? Not a good look, sweaty."

At that point, in the absence of being able to have a conversation with them to get a better answer out of them, I think the correct answer is to say fuck it and treat them as management, because they are treating themselves as management's protective shell anyway.