You mistake politeness for credulity. Einstein's letter is a bolw-off, rejecting everything about Velikovsky except for the obvious fact that there have been catastrophes in earth's history. Velikovsky was wrong about the dates, causes and scopes of the catastrophes, but then nobody's perfect.
Velikovsky was one of the first to propose earth changes due to catastrophic astronomical events, something we are all to well aware of now given the increased awareness of ELE events and the dangers inherent to asteroid strikes...and AE gives him credit for that right up front.
The truth of the matter is that Einstein considered Velikovsky a bit of a soul mate:
>Einstein often used the term "moshogoim" in reference to himself AND
>Velikovsky, the intent being not so much the literal one as "outsiders,
>wildmen" and so forth.