If you'd watched the segment, you'd realise there was a reason for it.
Specifically he used the segment to point out that Xi Jinping has more power and influence than almost anybody in China's history, that a personality cult has started to form around him, and that he is using that power in ways that has a wide range of long-term profound domestic and international consequences, including America's place in the World and perhaps even democracy's.
Yes, he used comedy. Yes, he referenced Winnie the Pooh and Xi Jinping's hatred of being likened to him. It's an entertainment show. The fact it is a comedy entertainment show doesn't make the point he makes any less true.
He had a point. He made it. China reacted to the point, not because it was a "random insult", but because if Chinese people watched that segment they may start to raise questions.
He was censored for the same reason that many other things questioning China's authoritarianism are banned from comments like this one I'm making here all the way through to many of the images at the top of this google search: https://www.google.com/search?q=tiananmen+square
Further, Oliver had used his show to make points about Trump, Obama, veterans, affordable healthcare, TV evangelists and a whole host of other social affairs using comedy to tell a story that would be hard to make entertaining using any other device. What exactly is your problem with that?
Just because you don't like his style of humour does not mean he is "randomly insulting people, countries or cultures for no apparent reason".
Also: next time, before throwing statements like that around, question whether you're doing it yourself. What _exactly_ were you hoping to achieve with this comment?