If your cat is hissing at strangers you can't stop your cat from hissing at them. The only thing I can think of that would stop a cat from hissing at someone is letting a cat get to know a person long enough that the cat isn't afraid of the person, and will therefore get along with him/her.
when your cat hiss does it hurt them
Hissing means that the cat is scared and it is trying to defend its self so stay away if a cat starts to hiss and arch his/her back.
Obviously, it didn't agree with your cat!
It usually depends on what type of scent they've found. If a cat starts hissing for no apparent reason it could mean that they have just picked up a different cat scent, for cats can be very territorial. If not, cats are usually just making the sound because they are either surprised or excited.
pick it up by its neck
pick it up and move it.
Some people think that spraying cats with water is good discipline but it doesn't honestly help. A hiss is a hiss as long as the cat is not attacking and/or being aggressive towards another cat. A hiss is normal and it is basically a warning towards the other cat. So to sum this all up, you don't really control a cat hissing, its natural.
See if the cat has ear mites.
Normally you would hear a hissing sound accompanied by your cat being angry
maybe your friend smells
yes