Your assumption, given to you by your Betters, is that extending the same tax break to all retirees collecting SS benefits will somehow bankrupt the system.
This is a calculus worthy of your pal, Marty the Waterhead.
The fact is that all those "evil rich" retirees your Betters tell you to hate...
I'm the Prosecutor. Once the Jury is selected and seated, I would present the case against tiny jack outlining all his hideous forum crimes against decency and goodness. Then the Defense Attorney - I think that's Xypoo - gets to present all the whiny excuses for tiny jack's perfidious behavior...