I live in Portland. Last year the voters in Oregon voted to decriminalize all drugs when in user level quantities. No one bats an eye when someone shoots up, smokes meth, etc on the streets. There are needle exchanges available. I’d say that’s fairly accepting, and the legal risk has been removed for the user. And yet the problem has gotten much, much worse. Why? Because people who are out of their heads on meth or nodded out on the street can have no meaningful interaction with the rest of society without disrupting it. Meth, at least in its current form, makes people confused, paranoid, and violent. No support system short of full on institutionalization can cope with that, and there is a mountain of case law that makes involuntary commitment extraordinarily difficult in this country.

There's a huge difference between styrofoam litter and used needles in terms of health hazard.