On one hand, there is a certain irony in giving official recognition to a religious community that was old when Caesar invaded Gaul. Next thing, we'll read that Utah has decided to recognize the Mormons.
On the other hand, let's be clear: these guys are completely bogus.
Oh, they're real enough -- unlike, say, many voters in Chicago or Kabul. And their religion is real enough, too, in the sense that it exists and is practiced. It's as real as Scientology, and a lot less bizarre. The modern-day druids (or, really, neo-druids) seem to be yet another amorphous nature religion, which claims for itself much the same territory marked out by Wicca. Fair enough. More than fair enough to get them some tax benefits, in our view.
What the neo-druids are not is druids. By which we mean that they do not stand in continuity with the authentic druidic traditions of antiquity - or that if they do, it is by accident.
Simply put, nobody knows jack-diddley about the genuine druids. Caesar came, saw and conquered some in Gaul, and wrote 'em up in Book 6, chapters 13-14. He made them out to be a caste of wise men who taught the transmigration of souls, judged legal cases, and offered sacrifices (including the human kind).
But Caesar, and the various other classical writers, aren't trustworthy witnesses. They rarely are with cultures other than their own. It is likely that the propaganda machine painted the druids to seem barbaric enough to need Roman civilization, and noble enough to be worth the effort. Modern historians seem to throw up their hands in despair, pointing out that we have close to zero archaeological or documentary evidence that can be definitively described as "druidic."
What we do have, to be sure, is a long history of Romantic myth-making, by 18th and 19th-century British writers, most of them minor and best forgotten. These are the guys who created, more or less from whole cloth, the sort of "druidry" that is now practiced in, and recognized by, Britain.
To put it in perspective, imagine that Christianity's deal with Constantine had not worked out. As a result, the great churches and monasteries were never built; the handful of Christian documents already in circulation were largely lost. No Epistles, no Gospels, and certainly no Eusebius. All that remained as a record of this obscure Asiatic cult were Pliny's letters to Trajan, a passage in the Annals of Tacitus about the Neronian persecution, a paragraph in Josephus. Heck, throw in the Alexamenos graffito, 2 John, and any one document from Nag Hammadi. (That's already more than we have on the druids.) Then try to imagine re-creating Christianity from those sources.
Here's what it might look like: a bunch of death-obsessed Jews with a "general hatred of humanity" worshiping Bottom from Midsummer Night's Dream. While praising the archons.
Still, it could get you a tax break in Britain.