It is showing dominance and claiming territory.
Why Do Dogs Kick Their Back Legs?
Dogs have scent glands on their feet so they do that to leave their scent behind for other dogs to smell.
THis is common and normal, they are just trying to spread their scent when they do this. He's just marking his territory that's all.
Its because you are not nice to you. They HATE you!!! HAHA!!! Not really it does mean that. If your dog or dogs have been tied up on a chain forever or a long time let them lose!!!! Or they will hate you forever!!!! Kidding but a dog like to be free if you have one and its chained up its not happy at all your not really for a dog if you can't train it to stay in a gate!