Does your definition of "harm" include the costs that society is forced to bear for any treatment you might require? (And, no, "I have health insurance" isn't an adequate response to that question. When your health coverage pays for rehab or whatever, my premiums go up, too.)
I maintain that "externalized costs" can be a violation of the Non-Aggression Principle. Under a strict interpretation of that ethos, you shouldn't get to unilaterally impose upon me any costs that I wouldn't otherwise have been obligated to bear, had you not engaged in $behavior.
From "Libertarian" premises, however, the solution to those costs is that smokers, drinkers, and people who eat poorly should pay higher healthcare premiums to offset the increased costs they incur.
The problem with that, of course (and a big part of why I'm pro-single-payer) is that people who eat poorly, for example, are disproportionately poor, themselves. It turns out, it's expensive, in terms of time and/or money, to eat healthily, and the poor, especially the working poor, tend not to have one or both of those to spare.
In point of fact, I'm an ardent believer in single-payer healthcare, and think it both tragic and (to the extent the notion of criminality applies to nation-states) criminal that the US is the only first-world nation that lacks it. So, yes, I do believe taxes can be very well spent in "help[ing] people".
I'm merely taking the NAP to its logical conclusion, and using that to argue against another Libertarian plank.
You don't have to support drone strikes, you just need to withhold your indignation when your taxes fund them, as opposed to drug treatment programs. Based on your posts here I'm pretty sure we're in 90% agreement or higher on both drug and health care policy, so I'm not arguing with you, but your OP could easily be mistaken for simple concern trolling. I doubt you pipe up in every thread discussing government spending, to "take the NAP to its logical conclusion".
EDIT: Thinking about it a bit further, however, I'd counter that piping up in every thread about government spending with, "But NAP!" would actually be the trollish behavior. It's contextually appropriate here, because my OP's parent comment was making a personal freedom argument — characteristic, if not stereotypical of Libertarianism — for the right of an individual to use whatever drugs they wanted.
One of my biggest criticisms of Libertarianism, as I've tended to encounter it (living in SF, and being regularly exposed to the somewhat unique strain of the ideology that thrives in Silly Valley), is that it often fails to recognize that you can't have rights without the responsibility to uphold those rights for others, and goes too far in the direction of "my" freedoms, without consideration of where the exercise of those freedoms might infringe upon yours.
Upon seeing yet another example of that, I think it's wholly appropriate to bring up the NAP and how, taken to its conclusion, that argument could actually become self-contradictory.
I also think it would be wholly inappropriate to bring up the NAP and drone strikes in a discussion of tax revenue being used to fund, say, national parks.
Well, yes it would be, and you're starting to get to the crux of why Internet libertarians can be so irritating :-)
But I'd argue that people who bring up NAP constantly at least have the "virtue" of ideological consistency. You can't really pick-and-choose with non-aggression, without quickly devolving into pragmatism i.e. "it's okay to force everyone to do X because it has outcomes most of us agree are desirable, but we shouldn't force everyone to do Y because not enough of us desire the purported result". If you're bringing up NAP (even as a devil's advocate) for one thing, but then conveniently not even showing up for other topics, or worse yet showing up but not defending NAP and instead arguing on consequentialist or pragmatic grounds, then really all you're doing is using the non-aggression principle as a tool to defend stuff you wanted to happen anyway. I guess maybe that isn't trolling per se, but it's certainly not arguing in good faith, either.