I'm surprised I have to argue about whether it's irresponsible to throw dangerous things into a crowd. It's irresponsible because they're dangerous.
He can't be sure what will happen with pills that people accidentally carry out on their shoes or clothing. Any pills that don't get cleaned up from the venue could be eaten by children or animals at a later date.
We're talking about a drug that we don't even let sick people buy until they've talked to a doctor and a pharmacist. Maybe someone in the crowd wrongly believes that they need it or rightly believes that they need it but doesn't know how to take it properly.
Also, if you don't have sympathy for an adult who eats homemade pills and suffers from it, then you're pretty much arguing that this whole plan is irresponsible from the start.