>One problem is that lots of people include tons of known harmless stuff under "bad chemicals" because it's "artificial" (even if it's chemically identical to "natural" things that they praise at the same time).
People who believe in homeopathy don't believe this, since they believe that purified water has "memory", so logically they would also think that naturally-derived and artificially-derived but otherwise identical chemicals would somehow be different from one another.
One caveat, though: the identity of chemicals needs to be pretty carefully defined. Especially any time chiral things are involved, naturally-derived things are much more likely to be a pure enantiomer or close to it while artificial synthesis is more likely to produce racemates unless you are very careful.
True, but even here we're not talking about identical molecules. Chiral molucules are ones (which are usually organic--based on carbon) which have both "left handed" and "right handed" versions. The two versions have the same molecular formula, but they're opposites of each other. So it's like having a left-hand drive car versus a right-hand drive car: they might look identical using a mirror, but they're really not, and you can't use them the same way because the way they interact with their environment is different (a driver in a RHD car in a LHD country will have a hard time seeing everything properly because the roads aren't designed with this configuration in mind).
People who believe in homeopathy don't believe this, since they believe that purified water has "memory", so logically they would also think that naturally-derived and artificially-derived but otherwise identical chemicals would somehow be different from one another.