In MY TIME (the '70s), a player was a guy (never a woman) who was trying to score sex from as many women/girls as possible. It was a competition (stated or unstated) with other 'players'. Free love, birth control (the 60's) and legal abortion (1973) were all REALLY NEW. A lot of the OLD RULES (from the 1950's and before) were thrown out the window...but nothing replaced them. It was kind of the Wild West of sexual adventure.
Since the goal was to bed as many women as possible, NOTHING was off-limits: lying, misleading, manipulating, getting someone drunk/stoned, etc. Women were just a piece of azz to be scored, they weren't people with actual feelings. I saw A LOT of people get really hurt...they were living under OLD RULES (under which we'd been brought up) that no longer existed.
So when guys say, "Don't hate the player, hate the game!" it makes me feel like threatening their manhood with a machete...but I don't.