This post misses the point quite spectacularly. We are not atomised individuals, we are all connected and our actions affect others. As
A380 points out alcohol misuse has high external costs in terms of violence, I'd add to that other forms of anti-social behaviour and accidents too. And perhaps the biggest impact is on the immediate family because contrary to popular myth most people with alcohol problems are not lonely old men on park benches. So we do have a duty to collectively try to manage addiction because of the number of people who are affected. And even if we were genuinely only talking about an impact on the drinker themselves, I still don't think that's a reason for simply abandoning addicts to their fate, as it's 'their own stupidity'.
It's not left wing to allow people to behave how they like no matter the impact on others, and it's not left wing to think it's fine for big business to design products that are basically designed to fuel addiction and profit from misery (eg the very cheap white ciders). I'm sure most of us wouldn't think it ok if a cartel was to flood the poorest communities with cheap opiates - we'd think it was a looming social disaster - and I really don't see the difference. I'm not sure the MUP is the best solution to all this, and it's certainly won't work by itself, but it's deeply depressing how many people view any restriction on alcohol at all as an outrageous assault on their personal freedom.