Complete humbug. Not just their doctrine, which goes without saying, but the claim that today’s “Druids” have anything more to do with the Druids of ancient times than both being located in the British Isles. Neo-Druidism is as much a modern made-up religion as L. Ron Hubbard’s Scientology.
Other than Roman descriptions, which are almost certainly unreliable (either that or the ancient Druids really practiced human sacrifice), we know nothing about the praxis of ancient Druidism, and nothing at all about its doctrine.
They did.
So did the Romans for that matter.