Wouldn't an intended side-effect of this action be the end-user getting educated about "why the device I bought doesn't work anymore?" and directly impacting the reputation of the company that manufactures that now-bricked device?

I can only see it as a win-win. Except the internet connected medical devices that are insecure which if affected by such purging bots would literally impact lives. I hope vigilante script kiddies don't get involved with good intent and cause havoc.