Tell him or her to speak to an employment lawyer if they don't already have plans to. These policies certainly seem to be in conflict with freedom of expression.
Obviously there is a balancing act between discrimination policies but the sense I get is these policies are more often used as a convenient method to dismiss employees.
In the meantime it is probably best practice to put as much distance and barriers between your social media and employers. Use of private profiles, alternate name/anonymity, no reference to occupation or employer in bio and don't give access to untrustworthy colleagues who could turn grass.
Should strengthen argument that you weren't bringing employer into disrepute if there is no discernible link (even with googling) between them and you.