Be Nice - a little Mama venting

Once a week this year my oldest child has had an after school sports activity where there are a lot of other children involved. Part of parenting is dealing with the wait time with the younger siblings. Keep them busy, keep them entertained, keep them from complaining they are bored waiting for their brother. I usually come prepared with a few toys (and a bonus one in my purse just in case) and a couple of snacks. There are of course other younger siblings waiting in the common area for their older brothers and sisters to finish sports so we can go. The younger siblings have been okay with this. As kids do they come up with their own classic games to pass the time: follow the leader, races and tag being the favorites. What I don't get is the parents who blatantly ignore the younger siblings all together. For me it's a no brainer, I can keep an eye on my older son's sports while still supervising my younger children. Many of the other mothers don't seem to see it that way. They take the time to gossip and text instead.
This can get increasingly annoying.  Often, I would take my 2 little ones to another part of the sports complex for a change of scene and to keep them out of the line of fire of the 'unwatched' children.
A couple of weeks ago, my kids were having a great time playing with these other kids.  And then this little boy came over and grabbed my daughter's arm and squeezed as hard as he could.  My daughter screamed and ran to me crying and said, "no like little boy" (they are both 2).  I told her she didn't have to play with him, just stay away from him, she could just sit with Mommy instead for a while.  My other child continued to play.  As soon as my daughter was soothed she wanted to rejoin the fun.  Well the poor thing, this little boy must have had some interest in my little girl because he ran right up to her again and did the same thing.  The mother paid no attention.  I thought about moving my kids but there was this part of me thinking, "why should my kids miss out on playing with other kids just because this one mom won't take responsibility?" So I gave it one more chance.
Sure enough it happened again.  This time the mother noticed my daughter crying, not her son grabbing and hurting her.   She asked me what was wrong and I told her.  Her response?  "Be nice!" to her son.  That was it.  "Be nice".  Be nice?  Seriously, that's it?  He's 2!  What does "Be nice" mean to him?  Absolutely nothing!  There's no consequence in that!  There's no teaching in that.  Be nice is a nothing!  So frustrating!  It was at this point, I took my kids and moved somewhere else.  I felt bad that my son had to leave his fun times with tag, but I couldn't put my daughter through that again.  I mean what else are you going to do?  It isn't my job to discipline and monitor other people's children.  That was two weeks ago, since then, I haven't bothered going to that common area at all (although my son would like to), we go somewhere else, where I know we aren't going to have to deal with that.  Seriously - take responsibility for your children!
Here's what would "Be Nice"
-it would be nice if you watched your kid
-it would be nice if you put your phone away
-it would be nice if you gave your kid a consequence for hurting my kid
-it would be nice if you took your kid for a walk so my kids could play without fear
-it would be nice told your kid to keep his hands to himself
-it would be nice if you said "no grabbing"
-it would be nice if you said "grabbing hurts"
-it would be nice if you were paying attention so you could stop your kid from hurting mine

 

*on a side note, I know I'm not the perfect parent by any means so I usually don't rag out about other parents, but this has been driving me nuts for a while and needed to be said!