How to prevent visitors from touching your system

On the way into the listening room everyone has to pass two full size racks for (electric) power supply and compressed air. Both are covered in meters, dials and lights. I tell them how much energy is controlled in each cabinet, and for some reason they scarcely even want to look at the equipment.

I just told them once and they remember

It's not cool to touch someone else's gear...   My lady won't touch my system but she doesn't have to.  She can pick up my Tablet and play anything she wants 

Years ago we had a party, actually we had three events back to back so I picked up a $50 pair of Klipsch so I could put my Revel stand mounts out of harm's way.   

Wouldn't you know it, one of my ex's friends put his plate full of food on the speaker and started to eat off of it ....   I looked at him and said.  " Really? You are using my speaker as a table?  The dining room is over there "   What a jerk.  So ignorant 

Ever heard of a company called Invisible Fence?

Buy extra collars.

Tell him you're Doberman will rip their balls off if they do lol, mine is trained to do that.