https://www.youtube.com/yt/about/policies/#community-guideli... - Hateful Content
http://itunespartner.apple.com/en/podcasts/faq ("Why was my podcast rejected or removed?") - Content depicting hate themes
http://itunespartner.apple.com/en/podcasts/faq ("Why was my podcast rejected or removed?") - Content depicting hate themes
The TLDR on these hate speech definitions:
YouTube: promotes violence against or incites hatred against protected groups
Apple: content including hate themes
Facebook: violent speech, dehumanizing speech, statements of inferiority, or calls for exclusion/segregation of people of protected classes
So it seems like YouTube's definition is the narrowest. Facebook's definition is much broader because it includes "statements of inferiority", and Apple's definition is vague.