At least at Safeco Field. And in front of uninformed heterosexual parents who would rather hide from their own fears and discomfort rather than explain the realities of life to their children. It's all so unfortunate and quite a silly fear. Kids can handle a lot more than people think. Keep it simple and straightforward. Don't over-react or add in a lot of unnecessary emotion and the child will likely simply shrug and think "oh, ok" and go about his/her business.
I would be more concerned with having my child witness ball players who chew tobacco or get upset over some call and have a fit on the field. And I would think it would be a little more difficult to have to explain the dysfunctional complexities of the class system, which come into play at sporting events. For example, those high class special stadium rooms.
"Mommy, why are there people sitting in that room behind glass? Why are people waiting on them like they do at restaurants?"
"Because they are wealthy, dear."
"What's wealthy, mommy?"
"It means they have a lot of money."
"How do they get the money?"
This is where the difficulty comes in. Mommy must explain that some people work and make a lot and others work and make very little while others inherit their money. The child will likely go on to ask if they can get some of that "money" so that they can sit in the room. Mommy will have to explain that not everyone can work and make that kind of money and not everyone will inherit a large amount of money. She will have to explain how the System works and will likely blow it all off in frustration, claiming "that's just the way things are!" while telling the child to go back to eating his hot dog.
The young child will never fully understand.