Continuity mistake: After Eddie questions what happened with Earl, his friend with a notepad writes "Laid off." But he grips the pad in a different manner between shots. Note the position of his index finger when he shows Eddie the message. (00:11:35)
Continuity mistake: When Eddie hears his friend has been laid-off, Delores puts her hand over the glass to remind him he needs to have the money by Friday and she takes her hand off the glass when the camera pans up to her face. When it cuts back to Eddie her hand is still over the glass. (00:12:00)
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 gets the camera from Dolores, the way he holds the camera changes in the next shot. (00:12:15)
Continuity mistake: When Angelo is messing with Eddie you see Angelo holding an egg. When Eddie grabs him you can see the egg is suddenly peeled. (00:12:55 - 00:13:05)
Continuity mistake: After Eddie kicks out the stool and forces a hard-boiled egg into Angelo's mouth, the eggshell fragments on the bar rearrange themselves into a neat pile. Also, two more eggs appear on the bar, which can be seen after Angelo gets on his feet and turns around. (00:13:40)
Continuity mistake: When Mr. Acme meets Eddie at the joint, he squirts the magic ink at him. The position of the things on his table keeps changing between shots. (00:15:45)
Continuity mistake: As Donald plays both pianos at once, the white piano's lid alternates from being closed to open between shots. (00:16:40)
Continuity mistake: During Donald and Daffy's piano duel at the Ink & Paint Club, the grand piano's lid opens and closes on its own while Donald is performing simultaneously with his hands and tail. (00:16:40)
Continuity mistake: In the scene where Valiant is sitting in the Night Club and meets Betty they start to talk. Notice she puts down her tray off to the side, in the next shot the tray is nowhere to be seen. (00:17:40)
Continuity mistake: When Jessica appears on stage, Eddie has Betty Boop standing next to him in all close-up shots, except for a wide shot of the public behind Jessica where Boop is missing. (00:18:15 - 00:19:05)
Continuity mistake: When Eddie is looking through Jessica's keyhole his left arm is down. When it cuts he is leaning his left arm to the wall. (00:20:15)
Continuity mistake: After Jessica's Ink & Paint Club performance, the audience gives her a round of applause. As soon as Marvin Acme stops clapping his hands, the shot changes - but now he's seen clapping again all of a sudden. (00:20:25)
Continuity mistake: In the scene where the gorilla is throwing Hoskins out of the club notice he is facing forward but when he lands in the trash he lands on his back. (00:21:20)
Continuity mistake: When Eddie Valiant gets thrown in the garbage by the gorilla he stands up and there is some trash on his back and hat, but when the camera changes shot the trash is gone. (00:21:25)
Continuity mistake: When Valiant walks out of the garbage and reaches to a window in front of him, the box and bottles next to it change positions between shots. (00:21:45)
Continuity mistake: After Acme and Jessica's patty cake incident, we see Eddie taking a stack of pictures from R.K. Maroon as Roger repeatedly bashes his head on the desktop. Between shots, Eddie's left arm immediately moves to his side. (00:22:45)
Continuity mistake: When Roger is blowing his nose, Eddie stands in the background holding a stack of pictures with his left hand (offscreen), but in alternating shots the pictures shift hands (widescreen only). (00:22:55)
Continuity mistake: When Eddie hands Roger the patty cake photos in R.K. Maroon's office, they look cluttered. Cut to the next shot and the photos are suddenly stacked neatly. (00:23:05)
Continuity mistake: After blowing his top in R.K. Maroon's office, Roger rests his head on the desktop. Watch how a black ledger appears beneath Roger's head by the time R.K. and Eddie walk over to comfort him a few moments later. (00:24:10)
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.