You saw a little boy playing on an escalator. Any misstep could be life-threatening. Would you let him be or stop him?
You may think that it was not your concern and his parents should have taken care of him. It can’t be your fault should any calamity befall him. After all, you have no malice aforethought. So, you let him be.
He ended up falling from the escalator with his legs severely lacerated. He fell because you let him fall.
In the same vein, it is no different from selling drugs even if you don’t force people to buy.
Letting an unfortunate incident happen when you can stop it is as nefarious as perpetrating the wicked deed.