A rate hike makes any further debt growth incurred by selling US treasuries start to go vertical in terms of domestic taxes needed to service the new debt. Any old debt bonds expiring and traded in for higher interest paying treasuries will explode our public debts beyond sustainability in terms of taxpayers being able to service that debt!
A while back that was my concern too but right now we got folks loaning the U.S. treasury money for no interest!
The fact is that this zero interest is not Yellen's idea, this is private traders who are buying T-bills with their own money.