Translation:Morality is the solid foundation of man.
Nah, "man" is just a more archaic/older-fashioned way of saying "human" or "humanity" depending on the situation. "Man" is of Germanic origin while "human" and "humanity" are from Latin via French.
"Men" carries a stronger association with males than "man" (which oftentimes is used poetically to refer to humans).
Sometimes people get upset over misunderstandings like how the word "man" in spokesman just means a person or human but they've come up with spokeswoman to "avoid sexism".