Well, perhaps one might look at it this way, if people are behaving in a negative way, maybe they bring, or attract, some kind of negative energy on or to themselves. Having said that, I’ve always had a bit of a problem accepting the notion of laws of attraction because, sadly, horrendous things happen to very good people. How do we explain that, then?
Re the saying “never trouble a druid”, I’ve never heard it nor read it, and I’ve done a bit of research online since you posted this, too, however, nothing has come up. I very much doubt it’s some piece of wisdom that’s come down through the ages either. It’s unlikely that ordinary folk knew much about, or had even heard of the druids, until the revivals of the 17th, 18th and 19th centuries, so it’s unlikely, in my opinion, that this saying represents some kind of folk wisdom.