Why does my cat do this?

OK so i have had my cat for 4 yrs and I have a room divider that is made out of the perfect nail scratching material unfortunate for me ... So he thinks its a scratching post ever since I got him but I deter him from scratching all the time.. I spray him with water, I stop him from doing it but he doesn't listen... Everytime when he is doing it and I walk by he looks at me like "what are you going do about it or he runs away... So he knows it's wrong to do but why does he continue to do it.. Does he feel like he owns it too and it's his.. LOL It's like he testes me.. UGHHHHHHHHHHHHHHH....