Why is this man untouchable?

No, he isn't untouchable. You just haven't gone to high enough authorities. I suggest you take the matter higher than locally. Contact the Better Business Bureau, Department of Consumer Affairs, the State Attorney, and any other consumer rights advocate. The police sub-station was incorrect. Forgery is indeed a criminal offense. Instead of trying to deal with the police, try contacting the sheriff's department. You might also want to contact the political representatives in your area. Please don't let this person get away with this. Good luck.