To keep a long winded story short: WDYD when another child hits (or pushes/throws toys at/kicks) your child. You don't know this child, nor his/her parents. This has happened a few times and the parents see it but don't ever intervene. If this happens, do you just remove your child from the situation or do you say something to the kid/parent. In my situation, parent supervision is lacking at best.
This has happened a few times. It makes me so angry when parents don't say something when their kids hit other kids.