I ***HIGHLY** recommend enabling "restricted mode" for kids on YouTube, go to account settings, look near the footer for [language] [location] [restricted mode] [history] https://twitter.com/a2_4am/status/1002582467340132352 …
...then starting with a small list of well-known hate-oriented channels and running some data analysis scripts to build a large list of "related channels", and putting all the results into the blocklist.