In two clicks I found their community guidelines on their website:
https://discord.com/guidelines
Second rule:
"Do not organize, promote, or coordinate servers around hate speech. It’s unacceptable to attack a person or a community based on attributes such as their race, ethnicity, national origin, sex, gender, sexual orientation, religious affiliation, or disabilities."
Calling someone a "retard" or "autist" is considered by Discord to be mocking people with disabilities.
Also IRC exists and is still in use by many people. Anyone can set up a server.