Not everyone can deal with the issue of herpes. I've found quite a lot of folks think it's much worse than it actually is.
Ironically, most adults carry HSV1; the strain that causes cold sores around the mouth. Most rarely (or never) have an outbreak. Yet they might treat genital herpes like it's the Ebola virus. Often this is due to misinformation regarding this virus.
Your former partner would not have a leg to stand on in a court system.
As tlkittycat has pointed out, HSV is not a death sentence. You were also honest with this person regarding your status prior to become intimate with them. It then became their choice to continue on in what sounds like an unprotected physical relationship with you.
Tell him you are seriously thinking of pressing charges for attempting to extort money from you over this matter.