my son watches tv all day

This is very bad for his developement, both socially and mentally. He is only four years old. You are the parent and you need to show him that what you say goes, even if he doesn't like it. You can't give in either, you have to be strong. It is for his own good. Try to substitute other things that will help keep him interested; like games, other toys, outside games, going to the park, making friends with other kids his age, coloring, read books to him. There are any number of things you can use to get his focus away from the televison. Best of luck to you.