Continuity mistake: After the alleyway scene, the cab jumps on a bridge. The first angle shows that there are no cars next to the woman with the pram, but half a second later, when the angle changes, there's a grey blue car behind. (00:59:35)
Continuity mistake: When Judge Doom is melting and is just about to die, the wide angle shows he's surround by a very thick cloud of yellow smoke that keeps us from seeing his face, then in the close-up it changes to a very thin smoke that allows to see his face, and then back to the wide angle and the thick smoke again. (01:31:55)
Continuity mistake: When the weasels make their appearance at Mr. Acme's crime scene their car knocks some boxes off. From one angle they are all scattered next to the front bumper, but when the angle changes they're gone and have moved several feet to the right. (00:31:55)
Continuity mistake: Roger and Jessica are safe when the spray-machine breaks the brick wall. It then goes through the other side staying on the left side and moving far away from the debris. Angle on Valiant, and when back to the wall the machine has suddenly moved several feet to the right and is crossing the wall again.
Continuity mistake: In the scene where Valiant leaves Maroon's office, he goes outside and closes the door behind him all the way. Then a cartoon character passes him. Notice the character opens the door by pushing on it instead of turning the knob? I thought Valiant closed it all the way. (00:08:45)
Continuity mistake: The number of wood slats on Baby Herman's playpen keeps changing at the start of the film. When his mom says goodbye there are eight slats at the front, and five at the side. When he escapes the playpen there are eight at the side, and when Roger realizes the playpen's empty, there are nine at the side and seven at the front. Additionally, the characteristics of the teddy bear changes, as well as the colors of the balls on the wood slats. (00:00:40)
Continuity mistake: When the officers are carrying Marvin Acme's gurney away, one of them bumps into a crate of squeaking shoes. As the crate topples over, its lid flips upside down between cuts. (00:30:25)
Continuity mistake: As Roger and Jessica get tied to the hook, Wheezy and Stupid switch places between shots. (01:22:15)
Continuity mistake: At some point during the opening cartoon short, Roger drinks a bottle of Acme chili sauce and flies directly into a wall-mounted ironing board. The ironing board has a handle on its left side - which vanishes between shots. (00:03:10)
Continuity mistake: In the scene where Valiant is in the bar and just learned that his friend has been laid-off he takes a drink but Dolores puts her hand over it. In the next shot she has a shot glass in her hand and a bottle, but when Valiant shows her the check, both the glass and the bottle are gone. (00:12:00)
Continuity mistake: When Eddie goes to meet Maroon with his accusations, Maroon is holding a distinctively brass colored gun. When Eddie attacks him, the gun is released by Maroon, and it instantly cuts to a shot of Eddie on top of him, an identical gun in hand. Then when they get up, Eddie tosses the gun aside. When Doom shoots Maroon through the window, Eddie dives for cover and once again the gun is amazingly in his hand. (01:06:20 - 01:07:15)
Continuity mistake: When Eddie gets the camera from Dolores, the way he holds the camera changes in the next shot. (00:12:15)
Answer: There's really a lot of possible reasons he hates other toons. There's a whole Roger Rabbit book and comic book series that explain Doom's background more. In the film, he's greedy and wants to destroy Toon Town to build the freeway to make more money. In human disguise he's also seen as merciless and is just punishing toons to maintain law and order, etc. Although that's just an excuse to kill toons as well. However, not explained in the film; as a toon he was cast as the antagonist in cartoon films until an accident one day left him thinking he was an actual villain (as opposed to just an actor playing one). That's when he began his life of crime, including killing Teddy Valiant. So his hatred of toons is more about him being evil and not a personal vendetta against them, like Blade's motives.