The people doing it honestly don't believe it's hurting anyone.

what does that mean to me?

Cloud seeding, Solar radiation management, etc. You're not familiar? This is one of the top Geoengineering websites that will make it clear: http://weathermodification.com/

Why is it poisonous?

Stromium, Barium, and Aluminum have negative health effects when ingested directly. You can double check webmd on the poisonous effects. But maybe they are spraying high enough and it's getting diluted enough that it is perfectly safe. That's possible. But we are part of a big science experiment that I never gave my consent to be a part of and that's a violation of ethics.

It's called Geoengineering: http://weathermodification.com/

Weather modification.