The Council has it’s own ‘Zero Tolerance Initiative’ for protecting it’s staff against physical and verbal abuse, and makes an interesting read, especially the part that says “Non-physical assault is – ‘the use of inappropriate words (including, but not exclusively, verbal/written/social media) or behaviour causing alarm, distress and/or constituting harassment’”. Take a look:
Are we not entitled to have the same policy?
Here is a suggested sign for your car perhaps (it prints in A4 size and you can cut in to two signs) – see here