How can we stop our cat from protesting?

My cat always poops next to his litterbox because he is protesting. He always wants to go outside and starts pooping on the floor when we dont open the door for him

He’s an indoor cat who can go into our garden, but not further because he has the cat flu that he can pass on to other cats. From preventing him to go to our neighbours, we always keep an eye on him when he goes outside. But thats not possible of we install a cat flap

He is healthy for the rest and he’s llitterboxes are both clean. But how can we stop his commanding us around and him protesting? Are we giving him too little structure?

How can we stop our cat from protesting?
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