Yes, but a stock market index is just that. It is intended to track stocks, not meth sales or the phase of the moon.

Most of these indicies intend to match the largest companies on the market - going up when they do and going down when they do.

If someone doesnt want that, they can pick a different index or invest in a managed fund. Companies like vanguard also offer custom EFTs where you can exclude certian companies if you want - probably the simplest option.

But then you cant complain if they go up and you miss out.

PS: Yes, there are several cannabis ETFs if you are into that kinda thing. look into MJ, WEED, MSOS, and YOLO.