The morality of the consumer vs. the morality of the supplier an interesting problem. On one extreme, we have the drug dealer relationship. The supplier is obviously more morally duplicitous, and the consumer is often pitied (at least in liberal, anti-drug war circles). At the opposite side of the spectrum, you have suppliers making entirely ok or even ok things selling them to bad people. Are fertilizer providers to blame for consumers turning their products into bombs? Obviously not (actually, I'm not sure legally, but common sense says no).

In the middle, you have a wide array of relationships. Is Coca-Cola to blame for the obesity epidemic? Are gun companies to blame for suicides or mass shootings? Is Juicero to blame for customers being dumb shits?

I think when you answer different examples, you get a pattern: when a supplier is selling a negative/zero value product but induces demand by playing off human weakness, then they're doing something wrong.

Juicero is playing off human weakness (the wealthy tech nerds' desire to be "hip" and "fit") just like a a fashion company plays off human weakness (by creating unrealistic representations that it goads its customers into trying to reach).