It was in response to a comment that stated the gist of Frankl's argument i.e. the change in outlook was a difference between persevering and perishing in the camps. The context is right there in the quotation.

To me, the idea that people died in concentration camps because they had bad attitudes is as nonsensical as suggesting gravity is a social construct. You might feel my dismissal needs more explanation. I respectfully disagree and this is a hill I'm willing to die on.