Aren't all toddlers are obnoxious and loud?! LOL. Seriously, it sounds like a phase.. a form of potty training "regression" where he's pushing your buttons to see what you'll do.
Stick to your guns and dish up some psychology of your own. If he makes a scene and refuses to use the potty, start removing privileges like t.v., games, toys, whatever you think will work. If he's doing this in public, tell him he'll have to stay home while the rest of the family gets to go out for errands etc. because it's not okay to act up in public when you're 4. Stress he's too big for that, and if he wants to be treated like a "baby" then you'll dig out his pullups from storage and tell his friends. If it gets to a point where he has accidents because of this, remove privileges.
He may get constipated doing this. Be prepared with prunes and fruit juices. You can even tell him this will happen and that if it gets bad enough, he may have to see the doctor to get some suppositories. Explain what those are. He might not like the idea of having to get those, or having to eat prunes to get regular. Also tell him, no playdates etc. because no one elses mom is going to want to deal with that..nor will his friends!
Last but not least, point out all of the big kids in his life and remind him none of them are acting like him. If he wants to be a "big kid" like his older brother, then he has to act like one, and that means using the potty like one.