system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why other sects of Christianity generally do not like Catholics.
gpt
At one point in time, the Catholic Church was the *only* church...in fact, the word catholic means "universal".

Every major branch of Christianity at some point in time broke away from the Catholics.  Not only did they disagree on religion, but it lead to centuries of war in Europe, with one king trying to change the religion of his country, and the next trying to change it back.  This has led to some hard feelings that endure today. 

Check out the Reformation and the Counter Reformation for more info.