Continuity mistake: In Valiant' office notice the whiskey bottle to the right of Valiant. Then Roger is about to sit in his brother's chair. While Valiant is yelling at him, look right in front of him the whiskey bottle is there, but then when he sits down the bottle is back at its original spot. (00:39:15)
Continuity mistake: After Roger springs onscreen from an underground pipeline at the Acme Factory, a steel grate is thrust high into the air, falling right in front of Judge Doom (however the shot cuts away half a second before it's supposed to hit the floor). But two shots later that same grate is seen falling from a much higher elevation again. It should have been lying on the floor at this point. (01:21:10)
Continuity mistake: When Roger starts reading Marvin Acme's will out loud, Jessica takes her left hand and rubs his head, but once the shot changes her hand is nowhere to be seen. (01:35:05)
Continuity mistake: When Benny the Cab approaches a bridge where the woman is pushing her baby carriage, the sun casts shadows at wildly different angles in alternating shots. (00:59:30)
Continuity mistake: After Greasy starts up the dip machine, the number of ropes tied around Jessica's midsection changes from two to three within a couple of shots. (01:22:30)
Continuity mistake: At the end of the movie, when the spray-machine breaks the brick wall with the word 'Keep Clear' painted on it, the first 'E' and the 'A' get destroyed, but appear rebuilt a second later.
Continuity mistake: When Doom writes on the bar's blackboard "Rabbit Dip" the look of the text keeps changing all the time: sometimes it's neat, others it's fuzzy, and others some letters are missing. (00:52:10 - 00:53:10)
Continuity mistake: When Eddie hitches a ride on the back of the Streetcar, only its rear power-arm is attached to the overhead cable. Later when Eddie jumps off and says "Thanks for the cigarettes", it has both of its power-arms raised. (00:10:10)
Continuity mistake: In the scene after Valiant gets rejected by the trolley operator, notice as the trolley operator is closing the door, Valiant starts to fold the check. But in the next shot, he starts folding it again the same way. (00:09:35)
Continuity mistake: In the scene where Hoskins is washing his clothes and hiding Roger notice that the weasel talking is holding a gun. Hoskins puts a bar of soap in his mouth and the gun disappears. Then when he comes back to Hoskins the gun reappears. (00:42:15)
Continuity mistake: In the scene where the weasels are in Eddie's office, when the other four weasels see their leader falling down the stairs, Stupid (the fat weasel) closes the middle drawer on the filing cabinet. In the next shot the drawer is open. (00:42:20)
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: At Valiant' office notice the bottle of whiskey on the table, right before he examines the pictures of Jessica and Acme, the bottle is about almost full. But in the next scene after he finds out that Roger is there he sits down and you hear him pour himself a drink. In the next shot the bottle is almost empty and he is holding a glass that only holds about a mouthful of whiskey. How could he pour that little amount of whiskey and lose that much? (00:36:00)
Continuity mistake: In the scene at Valiant' office, Roger starts reading the letter but when he jumps off the bed in front of Valiant, the letter disappears. (00:38:35)
Continuity mistake: Mr. Maroon talks Valiant into working for him, he has his head tilted sideways. A brief back shot shows the head straight, but the immediate front angle shows it tilted again. (00:06:55)
Continuity mistake: When Eddie is on Maroon's office pouring himself some bourbon, Dumbo shows up and scares Eddie, who throws himself on the ground. The camera then shows him and his empty glass, and the ground is dry. Where did the bourbon go? (00:08:00)
Continuity mistake: Near the end in the Acme Factory, the weasels tunnel through the wall and say "Toontown is on the other side of the world, boss". Understandable because of the portal link between the two "dimensions". But while the wall they're tunneling through seems to only have about ten layers of bricks, when the Red Car crashes through it, it alternates between one layer of bricks to three and back and forth. (01:18:00 - 01:32:30)
Continuity mistake: At the beginning when Baby Herman tries grabbing onto a clock's swinging pendulum, he stands on a box of Acme deadly mouse poison. But when the box falls over onto the countertop, its label vanishes. (00:02:40)
Continuity mistake: Baby Herman opens the faucet and floods the kitchen, but 2 seconds later there is no trace of the water. Since the rest of the mess that Herman and Roger cause (scattered cutlery, broken objects and furniture) does appear at the end of the gag when toon and real world combine, some trace of water should be seen somewhere. (00:02:30)
Continuity mistake: During the first animated Baby Herman scene, he throws away the lid of the cookie jar on top of the fridge. When the fridge crushes Roger, the cookie jar has not only managed to move from the fridge to the floor in a nano second, but also the lid is back on. (00:03:15)
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.