He never implied that "plumbers are dumber than IT guys." What he implies that your average IT guy would be more knowledgeable about things involving bitcoin than your average plumber. This is a safe assumption, because of the differences in what their jobs expose them to on a day to day basis.
He sure as hell proved the opposite with his response. The fact that he's an IT guy does not make him more knowledgeable about securing bitcoins. I'm not an IT guy or a plumber and I'm not afraid to store bitcoins even if they are 100,000$/piece. Just because he would be afraid and not up to the task doesn't mean a thing for his neighbour.
Considering the average person doesn't give a shit about bitcoin, and your average plumber doesn't do much with computers in his line of work, I think his assumption is a safe one.
Next time, don't make the assumption plumbers are as scared as you for holding some bitcoins. 
Ironically I would think it would show a lack of education about the subject if they're not scared. Scared, cautious types do a lot more to protect themselves, and bitcoins are easy to lose for the uneducated.
If they are educated enough, there's no reason to be scared anymore, but there's no reason for his plumber to be "not enough" educated, just because he's not an IT guy.
You're almost just as much of a cry baby as Joffrey Baratheon, except he didn't live next door to a plumber and wasn't an IT guy.
