The drug dealer was selling meth. Meth destroys people. And meth addiction leads to many robberies and burglaries. I think punishing this meth dealer is a net positive for society.
I don't think it's right to punish a pub for all problems caused by alcohol intoxication, but I do think punishing a pub for serving alcohol negligently is okay.
My understanding is one of the main reasons methamphetamines are so widely used and sold is because meth is cheap and easy to make compared to safer possible alternatives. That indicates to me that this seems like a market that needs regulation, not prohibition.
I'm not saying meth should be legal, I'm saying the drug market can be regulated to reduce harm. If that regulation means disallowing certain substances that do cause excessive harm, that's a good thing too.
You could replace meth with any sort of legal substitute and the statement would still be correct.
'The bar was selling liquor. Liquor destroys people.' 'The pharmacy was selling opiates. Opiates destroy people.'
So, when faced with a dilemma of hypocrisy like that, let's punish the wrong do-ers when they do wrong, as is traditional with substance abusers, rather than the 30 'criminals' involved in the supply chain that haven't actually done first-party harm to the peace at large.
One could say that they could be done in parallel, and I agree, but the resource spent to fight both sides of the crime in parallel should still be spent on keeping the peace, not preventing the imaginary destruction of future peace.