I'd be tempted to rig up an electric fence "barrier" and zap the git!
I do know how you feel though. We used to be on a huge livery yard and one of the farriers used to tie strange random horses up outside my stable and Asti hated it, got very aggressive when she's a real softy. And she started getting headshy.
Its just not on if someone is hitting your horse. One bloke let his gelding stop and sniff her bum when he was leading past - she just double barelled the gelding and I didn't apologise - he shouldn't have been so stupid!
Mind you, I have done the sickly sweet hello thing before, when you are being so pleasant they HAVE to reply even though they hate the idea... it does give some satisfaction!
have got my sign done ready to go up. This morning was hilarious as normally its steady x, woah x, don't bite me x etc etc basically a running commentary! deathly silence this morning and when I took Pidge out to the field he stood in front of his box protecting his horse and telling x it was ok - I had as normal taken Pidge the other side of the walkway as normal people do! Just couldn't resist myself and had a bit of a chuckle at his behaviour