This is so important, it deserves this highlighting:
Non-stupid people always underestimate the damaging power of stupid individuals. In particular non-stupid people constantly forget that at all times and places and under any circumstances to deal and/or associate with stupid people always turns out to be a costly mistake.
Oh dear god, none of you should ever, ever forget that.
Forgetting it will mire you in a trap that is near-impossible to escape.
Mike Cane’s xBlog 
Oh, my! Yes, it’s happened to me too and with far-reaching consequences. Sorry to hear you’ve been afflicted with this bane. I hadn’t seen The Basic Laws of Human Stupidity. Brilliant!