How do I deal with a situation where someone else's child is misbehaving in my house and the parent says nothing?

If the kid's parents are not stopping from misbehaving and if they are guests who will come once in a blue moon, let it go with smile, and you can rant later. But if he is your neighbour and they will visit you often, you will have to speak out when you find his behaviour unacceptable. If the kid's parents will not like it, they will probably stop coming to your home or stop sending their kid, which too is a good solution to your problem. And if they realise that you are right by trying to tell the kid to behave, then also it is fine. But any which way, you will have to stop the bad behaviour of the kid no matter parents like it or not.