It's impossible to get the informed consent of everybody in a public space who has to watch you. So no.
I don't go around asking the people in the park if they mind watching me play catch with my buddy.
Can you honestly not see the difference between that and having sex?
I can't, could you explain it to me?
Can you see the difference between raping somebody and starting a game of catch with a dog without asking the dog first?
Do you think that there's a right to have domestic disputes or rows in public?
People, taken generally, tend to view playing catch as completely inoffensive on every conceivable level. Extremely personal activities such as having sex or fighting tend to be viewed as having at least some of the character or aura of privacy about them. I'm honestly not sure how one can grow up in a civilization and not at some point realize this.