I feel like there is an answer for this, but why are two companies in the "YC family" at odds so publicly? If RapGenius is "starting beef" like is done in the m

I feel like there is an answer for this, but why are two companies in the "YC family" at odds so publicly? If RapGenius is "starting beef" like is done in the music industry, I find it odd that it would happen with someone on their own "label". Perhaps this is ignorance on my behalf of how companies who have already been sold (Heroku) fit into the picture, but some explanation would be appreciated.