Comment by CodeMage

As GP pointed out, "hero" is a word with overloaded semantics. I think Adams was using different semantics for different occurrences of "hero" in that phrase. Arthur Dent has a "heroism", as in a kind of courage that people would want to emulate, without being "heroic", as in performing great sacrifices for a noble cause.

I also believe Adams was trying to point out, very gently, the same cultural difference I called out in the comment I replied to, i.e. that the American culture attaches certain expectations and connotations to the word "hero" not because they are intrinsic to it, but because of American bias.