If a government was committing acts of genocide, do you believe private enterprise should be compelled to be complicit in these acts?
Besides, GitHub probably does offer services to the Chinese government bodies and it will be no surprise to anyone if it turns out they are committing acts of genocide against the Uyghurs. They are probably hosting code related to research and commercialisation of the facial recognition programs that various governments will be implementing.
To draw the line at Ice but not withdraw services from the Chinese mainland showcases the level of myopic politicisation that is being lobbied for here. They are a platform, they should act like one.