Well, the word hero is Greek, and it is used to describe those who commit a selfless, brave act in battle, etc. McCain did not actually do such a thing in battle, but his 5 years as a POW were a heroic period for him, for his resistance to torture, his strength of character, his refusal to be released as an admiral’s son, before his comrades, and his later embrace of his former enemies in recognizing their victory and heroic fight for their country.
These were acts of strength of character that most weasels who are pissing on him now would not even understand let alone be part of any of it.