Not all wasp sprays are the same. Some freeze, some are chemical agents. Some of those chemical agents are sub-derivatives of sarin; a nerve agent. Sooooo, you are shooting them in the face with something with a huge likelyhood of causing permanent blindness.

Second, you have to assume any less-than-lethal spray weapon is going to get in your face too. There is a reason they make cops get shot in the face with OC spray and take a ride on the lightning with a taser before they will allow them to carry it, especially any spraying agent. You have to deal with the overspray and fight through it.

I'm not a lawyer, but I think I would prefer to defend myself in a civil suit from a shooting over the wasp spray. The laws are more cut and dry, and intentionally blinding someone leaves a live witness that a jury can sit there and look at through a trial. I've just seen too many weird things in court to want a blind sympathetic plaintiff dirt bag suing me over wasp spray.

They make OC canisters the size of small fire extinguishers and they spray just as far as wasp spray. If your friend refuses to relinquish their adversion to firearms, this is what I would recommend.

Some people can't let go of their belief in humanity, society, higher powers, whatever... and see reality. They rely soley on the kindness of others as their only defense in life, as do we all to a certain extent. It works out most of the time, but you only have to be wrong once. Terminal victim attitude. I hope it works out for them, or they survive to learn the reality of the big ugly in the world. It's all you can do.