I agree that the kid selling it at the party was being extremely careless and should face legal consequences. That said, as someone born and raised in small-town Oklahoma, I can tell you that most Okies don't know the difference between marijuana and meth until they end up hopelessly hooked on the latter...which actually happened to about half of my graduating class.
Everyone SHOULD test their drugs before dosing, but the reality is that far too many people have never even HEARD of test kits and wouldn't know how to use one if they had it. Harm reduction is not taught in schools; in places like Oklahoma, the general consensus is that all drug users deserve to die for sinning against God. To give an idea of the ignorance level in the state: Not long ago, the local news dedicated a special segment to the dangers of "iDosing"--aka listening to soundwaves to alter consciousness. (See
here).
My $0.02: A more practical form of drug education is needed in schools to help prevent things like this. We learn to put condoms on bananas in 7th grade to prevent STDs and pregnancy but get virtually
no useful harm reduction info when it comes to drug education. Abstinence-only education doesn't work, period. Pretending that it does is like telling drug users they deserve to die. Hence my relentless obsession with
harm reduction.