It's bad because it has an effect on people that is a lot harder to hold off than most drugs used. Granted the person not the product is to blame, but it is a drug that has damaged and killed a lot of people and therefore affecting other people, who do not use the drug. A good friend of mine was a speed junkie and that was bad enough, midnight phone calls for money, not even a phone call sometimes a rock-up at 4am, asking for hook-up, borrowing large sums of money, and worst, a lack of care for anything or anyone around them. I'm not saying all heroin is the "evil junkie creating" style, as so the social stigma, but it has a grasp that even the most careful user can be susceptable too. If it doens't kill you, it's an addiction and if you beat it, sometimes you end up addicted on what you used to beat it (methadone). People that beat it and come out clear are amazing people. But the issue as you stated isn't the drug, but the person, therefore the question is, why play with something when, you could underestimate exactly how strong your sense of will or desire is? I'm not a blasher, believe me, I love my weekends, I just have a negative opinion against a drug that no good has ever come out of.
[Pleonastic]-I'm not arguing, it's just an opinion. I know my will power concerning the drugs I do use, I know my limits, I've tested them (for better or worse). But I don't test with things that I can't guarantee, especially when the effects and consequences, social or otherwise are known. The old man would be making an assumption on my character without knowing me well enough. I'd tell the old man "I don't have a habit." Then you'd ask define habit? A habit depends on regularity of use, correct? A habit controls you, subconsciously or otherwise.
I'm just saying don't tempt yourself with something, unless your positive you know how strong you really are. And how safe you feel in regards to what your playing with.