Not the original person you replied to, but as far as I'm concerned there are a few questions that could very easily indicate which side of the line is something.

E.g.

- Is it addictive?

- Does it have the potential to destroy lives?

- Does it have the potential to destroy lives in seconds?

- Does it have a strong lobbying mechanism behind it? (n.b. things that are good and nice rarely need someone to bribe people to accept them)

or simply:

- Would you be worried if your child did it?

I think the number of "yes" that you get draws a very clear line.