Why was Owain Glyndwr famous?

A surprising number of English people seem unwilling to admit that anything about Wales is real, so they might answer the question "Why is Owain Glyndwr famous?" with "because somebody made him up". This would seem to be a form of racism, since along with other gems about Wales, such as "The Welsh have no history - they just made it all up", I have also heard "Africa has no history"!

The same contributor to this website added: "and I have not ever heard of any one by the name of Owen". Well, I have just Googled the name Owen and got 184 million results!