Not taking sides but just putting out some facts using Vanguard Total Bond as an example, with $1m initial investment and $40k/year annual withdrawals adjusted for inflation... in all cases tested pretty good capital preservation given the defined income stream of 4% adjusted for inflation.
Last 10 years: Jan 2008 to Dec 2017... ending balance of $949,418
Last 20 years: Jan 1998 to Dec 2017... ending balance of $1,049,889
Last 30 years: Jan 1988 to Dec 2017... ending balance of $2,054,657
First 10 year period... Jan 1988 to Dec 1997... ending balance of $1,628,912
Second 10 year period.... Jan 1998 to Dec 2007... ending balance of $1,165,298
Third 10 year period... Jan 2008 to Dec 2017.... ending balance of $959,418
Most recent 10 year period.. Oct 2007 to Sept 2018... ending balance of $925,942
https://www.portfoliovisualizer.com...ividends=true&symbol1=VBMFX&allocation1_1=100