Good old Microsoft, just like any other commercial organisation, does nothing for the good of it. I am sure that the marketing spin of shutting the doors on paedophiles is good for the image, but in truth there are far more paedophile opportunities on AOL and Yahoo with their proliferation of unmoderated "neighbourhood" chat rooms than MSN ever offered.
If you look at their site information you will see that this withdrawal is not world-wide, and notably not in the USA and Canada. This move is about re-organising Microsoft resources to more profitable and lucrative revenue streams.
I will applaud this move if it does prevent just one paedophile pervert from contacting a victim, but we will never know that for sure. There needs to be a concerted effort in moderating the chat rooms, either by voluntary or, if necessary, paid for people. The trouble with that is that when (and it would happen) that the moderation fails, the individuals affected would be likely to sue the chat room operator. No chat room provider is going to take that risk and so they will remain largely unmoderated.