The "rationalization" that low rates justify high valuations is but one of several arguments used to justify overpaying for value in a late-stage bull market.
As discussed previously, one of the "bullish spins" for the market has been that "earnings are cheap" based on 2- and even 3-year forward estimates. As noted in "Justifiable Bullishness Or Is It Willful Blindness?":
"In 2020, investors are again chasing "growth at any price" and rationalizing overpaying for growth. Such makes the mantra of using 24-month estimates to justify paying exceedingly high valuations today,