Honestly given that China blocks so much of the global internet that it's easier to list off what isn't banned nowadays, this seems like a fair way of giving China a taste of their own medicine.

And yes, censorship is a big motivator in China's actions but I strongly suspect that the true #1 priority is to artificially prop up their own domestic offerings (after all the firewall is trivial to bypass). Blocking Google helps Baidu, blocking Facebook helps Renren, blocking Whatsapp helps WeChat, blocking YouTube helps Youku, etc.

I generally am strongly against governments restricting a foreign competitor just to help inferior domestic offerings but in this particular case, tit-for-tat.