Dogs don't inherently hate cats. With supervision and training, many dogs and cats learn to accept each other and even play.
Some dogs do have a very strong prey drive toward cats due to their small size and quick movements.
Dogs without early positive exposures to cats may view them as intruders on their territory, causing dislike or aggression.
If a dog has been frightened or attacked by cats in the past, they may be scared and dislike cats as a result.
Dogs who are possessive of their owner's affection and attention may become jealous of cats and act out because of it.
Rambunctious, high energy dogs can overwhelm or annoy lower energy cats with their attempts to play and interact.
Introducing dogs and cats slowly and rewarding calm interactions can lead to eventual friendship.