Timeless words of wisdom?

A quote from Greg Mankiw's blog

I don't care who writes a nation's laws, or crafts its advanced treaties, if I can write its economics textbooks.
-- Paul A. Samuelson

Samuelson did of course write the nation's economic textbooks, for many, many years. His first year economics text has gone through at least 19 editions. It was first published back in 1948. But what I wonder is how much damage has been done by having him do so. In particular with regard to macroeconomics.