"Hater" is an Americanism. It doesn't actually refer to "hatred": it just means "someone who can't say something nice about someone or something else" or "someone who finds faults with someone else because of jealousy."
Actually, in effect it usually
denotes: "Someone whose opinions differ from mine."
Its
connotation is to imply that such people must be twisted with rage and malice.
Its use is therefore actually more informative of the psychological state of the person using it than of the people of whom he uses it.
Edited by Dr Adequate, : No reason given.
™ Version 4.2