Emphasis instead of negation in 「そんなバカなことはありません」

Question

In this quote by Akihiro Miwa, 「そんな～ことはありません」 isn't used the way I'd expect it to be:

努力{どりょく}をしない人も[平等]{びょうどう}になどと、そんなバカなことはありません。
It's (extremely?) foolish to treat people who don't make an effort equally.

I think 「そんな～ことはありません」 is used for emphasis here, but is using negation in this way common and how does "there aren't those kind of foolish things" become "extremely foolish"?

Answer 1

そんなバカなことはありません has two interpretations in arbitrary context.

1. Literally meaning "those foolish things" are not existent.

2. It means that those things set a new precedent for foolishness. That is to say that it was unprecedented, or exaggerated to appear unprecedented. So one way to understand it would be to take it as "extremely foolish".

Answer 2

You are right that in your example, そんなバカなことはありません means “It is extremely foolish.” I think that the literal meaning of this expression is “There is nothing as foolish as such a thing,” from which the meaning “It is extremely foolish” follows logically.