Some Northern Mockingbirds think they own the neighborhood and everything in it.
Mockingbirds drive other type birds away from feeders and nest, attacking each bird as it arrives at the feeder or its own nest (not the mockingbirds nest) and even swoop in on an occasional bald head.
To put a stop to this territorial pest behavior is like a game.
Put your feeders so they are out of sight of each other, or have so many feeders the mockingbird can't deal all of with them at the same time.
But if that doesn't make you love him again because he no longer controls all bird activities in your yard, it becomes time to consider a drastic but likely a Federally illegal action.
Check the laws that apply in your community and if they allow it, kill the bird with an air gun and tranquility will return to your bird watching and feeding.
If you do not have shooting as an option, just keep moving the feeding stations and next year, the mockingbird may decide to be king of the hill somewhere else.