Ok, well, I think we know H isnt a drug you just 'stumble" upon.
Interesting of you to say that, while I had tried other opioids before heroin I actually did just stumble upon it. I was walking to my friends house one day when I saw a peculiar blue wax paper package on the ground. Upon closer inspection I realized it was five wax paper squares bound by an elastic, five bags of heroin. I took it as a sign and eventually snorted them all. It was wonderful.
Then a few months ago a friend of a friend found a bundle of heroin and some cash, so I got some more free heroin.

On to the topic though this whole controversy is bullshit, like politics. Some natural chemicals are poisons; nicotine, strychnine, atropine to name a few. Some naturally occuring chemicals are addictive; nicotine, morphine, cocaine to name a few.
Most synthetic drugs are derived from those found in nature, our knowledge allows us to alter the structure of these chemicals to produce new chemicals. We call this chemistry.
Plenty of synthetic compounds are safe enough for human consumption, just as plenty of natural ones are dangerous.