Of course back then it was unthinkable to be openly gay, especially in a workplace. And the scene with Kitty is amazing, when she first starts figuring it out. A line that cracked me up about this was Don and Betty sitting in bed talking about Joan Crawford. Betty goes on about Crawfords' eyebrows looking like caterpillars, and Don responds.
The meaning of the slang term “chaser” means that someone seeks out partners for romantic and sexual relationships based on one particular quality that a person has.