> So no, you should not take something merely because it's "probably harmless"

You and I should not. But I'm also not going to bother correcting someneone taking homeopathy for a cold. It doesn't do anything. But unless it contains heavy metals, it also isn't hurting.

You are strawmanning what he said. What he said is much better summarized as if a substance has other beneficial effects and there is one that is potentially just placebo, then it is ok. That is completely different than your paraphrase.