The text of that wonderful sign all the way to the right (no, not the one for loose fitting underwear, the symbol of a real gentleman, the one on the other side):
“Base Ball Players are all human, and therefore love applause. If you want a winning team, root for them, speak well of them to your friends, and while we are here let us all be clean of speech — so that the ladies may find it pleasant to come often.”
As someone who has never really understood the appeal of booing for a player on a team you’re cheering for, and really, finds the concept of wishing ill-will on another human being bizarre and cruel regardless of the circumstance, I find myself quite in support of this sign. Sadly, it, just like the Federal League, never seemed to take off, ladies or not.
(image of Washington Park in Brooklyn, Opening Day 1916, via NotGraphs, full text of sign via covehurst.net)