Really good post and based on what seems like substantial informed and highly educated personal experience, which is what people need.
I have never touched meth, not knowingly anyway (how do you know what you got in pills not tested?) and although this might make me sound dumb to those who will raise their eyebrow to my personal observations, the stigma of meth in the UK is very different to the stigma of meth in places like the US. I have never really witnessed it unlike cannabis, psychedelics, crack, heroin etc. It wasn't really in our vocabulary growing up. We know about smack (heroin) and we would attack anybody who was a 'smack head' or 'looked' like one. Anything other than meth was mentioned.
That being said, amphetamines have real value. The trouble is their affinity for addiction, like mentioned in OP. I had several years of craving speed and I can attest to how this less powerful version can wreak havoc on your life. One bomb turns into two into three. Luckily for us our supplier was illusive and because he was on speed often he was never in one place and never answered his phone and always had a distant relationship with his customers (probably the best dealer when I think about it) so this discouraged us to chase him all night so we would just come down instead and be forced to get on with reality. Then he would text us when we flat-lined and seconds from hitting some ZZZ's and the thought of coming back up was beyond us at that point.
When used appropriately, they can do some great things. And if it was used appropriately, less harms would result (obviously). Easier said than done.
I can imagine meth is no different. We just foolishly tarnish all drugs with the most extreme scenarios and we don't factor in what remains in the middle. That is, again like mentioned in OP, conditioned responses, or better put, reactions, to the war on drugs narrative. We need to stop that and we always have needed to stop that.