Why does lewis thomas express concern about what we would say to beings from another planet?

Mr. Lewis Thomas was an American physician, poet, etymology, essayist, administrator, educator, policy advisor and researcher.

Many of his essay discuss relationships  among ideas or concepts using etymology as a starting point.  

Mr. Thomas thought about the beings from another planet  that we are an ignorant species. This is the why we do the experiment.

king hrothgar despair over the inability to defeat grendel