Parental Q&A
This is a very common and very normal scenario. Let's see if we can figure out what's happening here. Your little guy has learned an exciting new way to push your buttons, this time by merely saying three little words.
It's likely at this age he doesn't really know what "I hate you" means. What he does know is that you think it's a bad thing to say and, when he does say it, people respond in a very intense way. Sure, it's not a positive response, but that's beside the point, because generating any intense response is fun.
Think about it. The world of a 4 year old is generally one of powerlessness. You have to eat and sleep what your parents say. They choose if you go to school or stay home. They pick your clothes. They explain to you how the mystifying world works. You're pretty much dependent on them for everything. There is very little over which you feel you have much control.
Then you find some simple words that confer onto you a power that is as irresistible as it is rare. Therein lies the fun. Of course your son doesn't really "hate" you. If you responded the same way if he said, "You're a potato," then that's what he'd be saying when he became frustrated. By the way, this is the same story when children begin to use swear words. It's the response they're looking for -- they have no real idea what the words mean. Fortunately, it's a habit easily broken by simple ignoring. If no one moves a hair whenever he says, "I hate you," -– no response, no acknowledgment, no anger, no time-out, no laughter, nothing -– as if he hadn't said anything at all, the fun's over. Soon he'll stop saying it. Of course, then he'll look to other creative ways to gain a measure of control over his world, so be prepared for what he comes up with next!
(Source: WebMD.com)