/johnny
If you can inquire about drug usage to determine if the other person is fit to do business with, then they can just as legitimately inquire into your fidelity in your marriage, for someone who will cheat on a spouse will cheat on everyone. Same for religion. Might ask well answer all your misguided prejudices in one sitting.
The only practical, non-offensive way to deal with people is to look them in the eye & talk to them. If they sound/act like an intoxicated fool, then go somewhere else.
The reason this is all so moronic is the incredible hypocrisy & shear ignorance about a recreational drug so much safer than the recreational drug alcohol.