[JackFr]

The fact that the author believes it is against LinkedIn's terms of service, terms of service to which he has explicitly, voluntarily agreed makes it unethical on its face. (Even if the terms of service don't prohibit this behavior, the fact that he believes they probably do is important.)

It's certainly not a grave matter in and of itself, but he doubles down by publishing a post to encourage people to join him in making a promise in bad faith.