No you are not being unreasonable Humdrum. Guitars and other equipment cost a lot of hard earned money with all of it being overpriced.
I would never touch anyone else's guitar without asking first and even then I wouldn't ask someone I didn't know very well.
I have been called miserable out on gigs because I don't like anyone touching my gear. A lot of people are not careful enough and a lot of the time are drunk so they don't know what they are doing. If you mention about what it costs they sometimes say, 'Why do 'YOU' wan't to pay that much for a guitar? it's only a piece of wood to hold the strings on.'
Obviously they are ignorant with no knowledge of guitars or equipment.
Now that I've retired from gigging I keep my guitars upstairs in their cases to be on the safe side. I don't mind other musicians that I know touching or playing them but I wouldn't even let them borrow them outside the house.
Visiting children can be a problem as giving them a clip around the ear and made to sit still is no longer done, (pity).

Also puppies can chew things like pieces of wood and they don't know an expensive guitar from a piece of driftwood.
If you value your guitars keep them out of the way, some people who I've only recently known don't even know I've got them.
