First world problem here. I make a birthday sign for my daughter and hang it up at the game. Security comes and takes it down. We don't want to "damage the stadium". Huh? Perhaps pay a little less attention to this and maybe try to keep drunken idiots off the field.

Where did you try and hang it ? if its over an Advertisement they will ask you to remove it if not there should be no issues
And How did you hang it