Here's how I back that up. Assume you have a teenage daughter. Now assume your daughter goes to a party and the host gives her either:
a Twinkie
or
some meth
As a parent, would you not mind if it was meth? Do you really think the impact on her life, her health, her state of mind, etc. would be about the same whether it's a Twinkie or meth? Or herion? Cocaine? Now how about if it was a Diet Coke? Or a glass of wine? I bet most parents wouldn't worry as much about the Diet Coke (even though it has "drugs" in it, like caffeine). And some may not mind if it was the wine -- especialy if just a small amount -- but of course even then, you would be more worried.
I think the difference is in how extreme and how fast the bad effects are, comparing a Twinkie to some meth. And while the Twinkie may not be ideal for your body, it almost assuredly won't make you go crazy essentially -- it won't mess with your mind -- like meth, cocaine, heroin, etc. would.
Now if you said, "Put down the meth and the case of 500 Twinkies," that I could agree with you on!
Put the Twinkie down and come out with your hands up.