Earlier quoted context omitted.
a euphemism for sure
Is it though? The word "abuse" is pretty strong. If I'm abusing substances it's not like I'm just having a puff now and then do I? The term "substance" is a bit generic, I grant you that. But does that make it an euphemism just because the exact substance is not specified?
we can agree on that, but the phrase has been bandied around in the legal/law-enforcement community enough that it's clear that the definition is generally : if it's illegal, it's always abuse. If it's legal it's only abuse if Uncle Bob is nodding off at x-mas dinner and stumbling into the tree.
There seems to be a strong inclination to 'help' the people that are generally a nuisance to other people -- which is to say that the 'help' provided is a way to keep the social status quo for others, not to provide the 'substance abuse victim' with support.