Well first off he isn’t a Druid. He may call himself that but they died out a long time ago. Most of them didn’t make it out of the pagan Roman era (outside of Ireland anyway). Those that were around during the early Christian era and the Dark Ages either died out or actually converted to Christianity. Many Druids and Bards became Christians in Ireland and Scottland.
To this day one our best sources for Druidic lore are the Chronicles of Julius Caesar’s conquest of Gaul. Even that is barely trust worthy as Julius probably exaggerated a bit so as to appear more heroic and his enemies more noble. The Roman people truly loved epic struggles between noble and well matched foes.
I’m not saying everything that was written was incorrect but the point is we really don’t know. All we have on the Druids is legend supplied to us by the eyes of foreigners.
All the modern day Druidic practices are propagated by groups that broke from the Golden Dawn or are in reaction to those groups. Some Wicca groups claim to practice Druidic magicks which is humorous since that Wicca is itself a Saxon term and Wicca tends to be a religion that focuses on “The Lady” (goddess centered). So it seems unlikely that it has anything in common with a Celtic, male dominated, solar (read: masculine) religion. In the end the mystical tradition this guy follows really can’t have any organized history that goes beyond the 1950’s.
Also many of the current ethics and mentalities of the modern neo-pagan is influenced by Christian ideals and moralities (like not holding the cast system of the brehan law). Sometimes when I see some of these more zealous neo-pagans I’d like to jump into Mr. Peabody’s Way Back Machine and take them to see some old school Skalds and Druids. I think they’d find them less romantic than the crystal rubbing, Enya listening modern equivalent.
Of course all of this aside. You could just take the approach that if he gives you to much lip you’ll chop down his grove, sanctify the ground and build a Church on top of it! That should get his attention.