I didn't realize this, but then again I played youth sports back in the Mesozoic Era. When an exasperated coach called us "sissies" for not trying hard enough, whining about routine bumps and bruises, or (in baseball) not sliding, they were, according to today's ignorant PC police, hitting us with an anti-homosexual slur. Horse manure; no they weren't. They simply didn't want us to act "timid or cowardly" (Definition 2 at Dictionary.com), two traits which are not positives in competitive situations.
In researching this post, I learned that the PC police succeeded in excising the idea of calling any single person or specifically named group of persons a "sissy" or "sissies" from civil conversation five to seven years ago. What I didn't realize is that they object even if the word is not directed at specific people. That explains why Cincinnati Reds Hall of Fame baseball announcer Marty Brennaman became a recipient of their ire on Wednesday.