I disagree, looking at the extremes is often used as a scare tactic against certain changes. We can also say that if we tax work 100% nobody would work.

The point of the OP was that work is generally more valuable to society than capital gains, but is taxed higher so there is a mismatch between the worth and how we tax it. Saying if we tax capital gains 100% nobody invests, does not add anything to the discussion as the same argument applies to work.