Would exterminating pensioners reduce the national debt?
if by “pensioners” you mean people collecting social security benefits it would not really change the “debt” directly but it would lessen the load on Social Security delaying it’s inevitable collapse. You could make the same argument about the people that collect welfare benefits as well or anyone collecting unemployment benefits or anyone that consumes more in public benefits than they pay in taxes. it’s still murder regardless of which group of people you are talking about.