Not exactly, the chaos caused by those tribes was short-lived, and they didn't play any major part in the hampering of scientific advancement. I would also like to point out that Rome wasn't exactly totally Christian. Rome never really subscribed to a single religion, it was always a mix of several, though Christianity certainly prevailed after its golden age. Hell, if you look at it that way, you'd come to the conclusion that Christianity caused the fall of Rome, which naturally isn't true.
The point is that Christianity in Rome post-Constantine didn't seem to completely and utterly ruin scientific and philosophical advancement in Rome.
The tribes didn't directly attempt to destroy scientific knowledge, but in addition to the obvious fact that a good number of learned documents were destroyed in the sacking of various Roman cities, they caused a society that had aspects naturally conducive to philosophical and scientific advancement(established universities, infrastructure, a stable government) to be replaced with a society that was less conducive to learning(lots of internal fighting, less infrastructure, a volatile feudal government, very little established system of education). Add to this the fact that the Franks and Goths were for the most part less advanced in philosophy and science than the Romans and you have a recipe for a dark age.
So really, Christianity saved the so called "dark age" from being the "total blackout age."
Completely and utterly false.
You have forgotten one very basic thing: Taking into account WHAT the church taught, and especially what it didn't.
The Church of the Dark Ages deemed all knowledge that was obtained after the bible was written to be the work of Satan, which is why technology and culture fell so low. It also declared all scientists heathens, and prosecuted people for terrible things such as trying to find new ways to cure illnesses.
And yes, they saved books, but only the ones they liked. Many great works were lost in the fires of the Inquisition, not to mention some of the people who wrote great works.
This section of your post just shows that you don't know what you are talking about.
The type of education pursued in monasteries and churches was something called Scholasticism. One received instructions in the subjects of the trivium: grammar, logic, and rhetoric, and the quadrivium: arithmetic, geometry, music, and astronomy. Certainly God and theology were seen as the center of learning, but this did not cause education to neglect logic and science. In fact, proper theology was supposed to be grounded in logic and science, hence the trivium and quadrivium.
They especially focused on Greek philosophy, much of which had not been preserved in Latin, and has been lost until rediscovered during this scholastic period. Plato was especially important, although during the Renaissance and Enlightenment, Aristotle would become more popular.
Additionally, contact with Arabic populations in both Moorish Spain and during the Crusades resulted knowledge of mathematics and medicine being transferred from the Middle East to Western Europe.
And at the center of this were monasteries and churches, as they kept and scribed books and served as centers of education until universities started to flourish in the 13th and 14th centuries.
People such as Boethius, Abelard, Aquinas, and Albertus Magnus made many contributions to various fields of natural science, philosophy, and fine arts. Magnus was even known for arguing that religion and science could coexist peacefully.
There have been throughout the history of Christianity persecutions, although the worst of it(including the height of the infamous inquisitions) didn't come until the very late Medieval Ages and Renaissance, when the Catholic Church found its political position challenged.
Still, to claim that the Dark Ages could have been golden if only the Catholic Church hadn't been around, or even that they would have been better at all ignores historical evidence is and thoroughly incorrect.
How does it ignore it? The chart simply points out that if it wasn't for Christianity, the Dark Ages wouldn't have occured, and technology would've advanced. Now, you prove to me that Christianity has resulted in scientific advancements big enough to excuse what the Church did in the Dark Ages.
Christianity was still very prevalent both before and after the Dark Ages, especially during much of the Renaissance, yet it didn't "ruin" them. Why?
Honestly, I think you could make a better argument that the Renaissance or Enlightenment could simply have resulted in more advancement without the Christian Churches than that the Dark Ages would have been less dark without the Catholic Church.
If you would like to continue to support your thesis that Christianity ruined the dark ages, perhaps by saying something more than "they persecuted people" without any specifics, showing how the Catholic Church explicitly destroyed the knowledge and technology of Rome, and demonstrating why the scholarship and writings of church and monastery educated philosophers, artists, and natural scientists either failed to contribute to or detracted from culture and scholarship as well as why civilization would have been better off without them, I would be interested in seeing how you are going to "prove" your argument.
And of course, the other glaring question: who else was equipped and would have been motivated to value education and preserve and scribe writings if not the Catholic church?
On the topic of Dawkins, it's not really possible to make a rigorous case showing that God must or must not exist. Dawkins puts forth his best attempt to show atheism is correct, just as Aquinas and Anselm of Canterbury put forth their best philosophical attempts to show that God must exist. Ultimately, neither have done much to appease those on the other side of the debate and have mostly only given ammunition to those who already subscribed to various sides, and none of the cases is strong enough as to even come close to settling anything.
I assume you haven't read the book, you should, along with "In the name of the Rose," a novel written by Umberto Eco. It peovides more details on the time period we are debating. ;)
Personally, I think David Hume did far more as an atheist philosopher than Dawkins. Maybe if you read "Summa Theologica" you will be convinced that belief in God is the way to go, but I doubt it, and I would be surprised if it convinced anyone at all who wasn't already inclined to believe in God. The works that the likes of Dawkins and Hitchens have presented us with in recent years are much the same in my opinion.