I am a registered greyhound trainer, one of my dogs is syndicated(a small syndicate of four). One of the syndicate is a QC, he has been interested in the allegations made by your "good acquaintance" and is of the opinion that they are actionable.

I never make threats, I make promises, and your "good acquaintance" would be well advised to apologise forthwith.

I allowed his/her remarks to pass in the first instance, but my good nature is not limitless.
Contact him/her and inform him.