Showing sexual images to a kid and showing him violence are not the same thing. These kids probably saw more violence than they should have at their age, but violence is simply a reality they will have to face sooner or later, and learn to meet with even greater force. Sex, on the other hand, is and should be private, while violence just doesn't have that element. We teach our kids, hands-on, how to shoot or how to take down an attacker, but we don't sit by the bed and coach them through their first sexual encounter. At least I hope you all don't.
We DO walk our kids through sex. At least I hope we all do. No, we may not be there in the room with little (actually not so little at this point) Timmy and Sally when they go at it for the first time. But our lessons, teachings, and advice damn well better be there in that bed with them.
Trying to prevent your son from seeing naked girlie pics is a senseless exercise. If he has half a brain (or any friends with half a brain) then I guarantee he's already managed to see some. If your little chillen is a daughter, then it doesn't matter. The bottom line is that there isn't much harm in him or her seeing a page or two out of Playboy magazine.
Now, the fact that a grown man is in a playground passing around pornography is a serious problem, an indicator that he's up to no good. YES, protect your children and your neighbors' children from him. But be an adult about it. Be responsible and set a proper example for your children.
Yes, we do teach our kids how to defend theselves, and how to kill if necesary. We teach them HOW to use violence. But we also teach them WHEN to use violence. Violence is only appropriate to prevent an immediate threat, and even then only if there are no other convenient alternatives. The sight of a naked woman on a page simply isn't an immediate threat. It doesn't merit a bloody response.
Run the guy off. Make sure he KNOWS, deep down, that he isn't welcome. Rough him up if you truly think that that is the only way to pretect your children from him in the long run. But for God's sake, be responsible enough to do it away from the view of the children. They don't need to have their faces rubbed into the harsh realities of the world. Let them be children, innocently playing in the playground.
Protect them, using violence and force if necessary, but let them remain happily oblivous to the uglieness that might have ensnared them that day.
