Well, he was partially right. Some of voodoo magic is chemical or potion based. See for example zombie powder which is actually a combination of drugs (one to induce a coma in a death-like state and another to make the person pliable and open to suggestion in a trance-like state).
Now if he was talking about voodoo dolls and curses? No, that's bunk. They only work on people that fully believe in it, giving a huge placebo effect that has been scientifically researched and documented. In fact, one scientist when confronted with someone "cursed" and suffering from a life threatening placebo effect had to "uncurse" the man, "curing" him by convincing him he wasn't cursed any more. It wasn't the curse itself that was killing him, but his belief in the curse was so strong that his brain was shutting down his own body.