All I can say is you must be fecking mad.......
If he dont like paying for your services and knowledge then tell him to buy some lego, build a bridge and get the feck over it. As everyone else will want payment, whether it be mates rates or whatever.
I'd like to see him pull that stunt in a petrol station or supermarket. He's obviusly not a mate if he's throwing that kind of shit around and taking blatant liberties of your good nature.
Tell him to feck off!!!