You're confusing homeopathy with herbalism. Herbalism is dangerous not so much in that it has no scientific plausibility (many drugs are isolated and purified from plants) but because it appeals to the naturalistic fallacy and does not take into account bio-availability. An herb will contain the active ingredient, the chemical that is actually causing the desired effect, along with numerous other things, most inert, some that potentially could cause harm.
The other dangerous aspect, and this is where CBD oil comes in, is that it's supporters often try to oversell how effective it is, turning into some sort of miracle drug despite a lack of evidence. That isn't to say it has no benefits. I think it actually could be very useful for certain symptoms and diseases. But what those benefits are, the situations it should be used in, and its mechanism of action, require rigorous studies before you go around claiming things about it.
Edit: Here's a study published in
NEJM describing a positive effect of cannabinoids in epilepsy.
https://www.nejm.org/doi/full/10.1056/NEJMoa1611618#t=abstract And an accompanying editorial:
https://www.nejm.org/doi/full/10.1056/NEJMe1702205
I will in particular highlight the last paragraph there: