I’ve been looking around on the Web lately, and a number of the usual sources (Wikipedia, term papers you can pay for, etc.) are convinced that “Dream of the Rood” is less Christian than pagan. Or that the pagan elements overshadow the Christian ones. Or that the poet’s POV at the beginning of the story is that of a pagan. Etc. A lot of these writers aren’t Christian, of course, so it’s possible for them to misunderstand enough to believe this. But then, this sort of thing actually leads some Christian people to think it’s a poem of tree idolatry. (Because obviously any Christian Saxon must have really still been pagan, especially if not a member of the reader’s non-denominational church established yesterday.)
On the other hand, you find a lot of the non-usual suspects loving this poem. Whatever they may think of the Catholic Church, these people understand things like evangelism, imagination, and the hard work of teasing out which strands are just another culture and which are inextricable with another religion.
I did see it pointed out elsewhere that, only a hundred years after this poem was written, St. Boniface and half his royal Saxon family were mucking about in Germany, establishing convents to be centers of Christian life, traveling trackless forests all year while evangelizing real tree- and pagan god-worshipping pagans, cutting down oaks that were objects of worship, and (in Boniface’s case) getting martyred by said folks. It is highly offensive to claim that such people, on the front lines of Christianity, were somehow not Christian enough and were really tree-worshippers.
There were probably still a good few pagans around in England when the poem was written, but unless it was VERY early, the real power of paganism in England was gone. (At least until the Danes moved in, and that was a slightly different denomination.) 
King Penda, the last pagan king (who had no objection to missionaries if in the right mood) died in 655. St. Boniface died in 754. The Ruthwell Cross, upon which some lines of the poem are written, is from about the same time Penda died.
To my mind, the “Dream of the Rood” is not something written by a brand new convert. Such a person would usually tend to be allergic to anything too close to his old pagan ways, eager to learn the new stuff. An experienced Christian wrote this thing, I think, someone able to play around a bit without fear. The dreamer’s POV is not that of a pagan, but of a Christian being further evangelized about stuff he knows. And the Rood’s POV is not that of a tree demanding worship, but one itself worshipping God. The Rood is acting as a friend toward the dreamer, not as a god. It’s not asking for the dreamer to slaughter any horses or cows for it, and the dreamer isn’t saying that he will. The whole thing is no more pagan than Ben Hur, being part of the long tradition of imagining the events of the Gospels in your own way.
And if anyone can’t see past the charming literary devices to the majesty of Jesus Christ depicted therein — well. That goes beyond “can’t see the forest for the trees”. It’s more like “totally blind and deaf to meaning and poetry”. Very sad.
