Yes and no. Let me explain...
Yes, it is. I say this because everyone is entitled to their own opinions and views, however misguided and wrong those views may be. If someone wishes to blame a religion for a lack of scientific development at one certain point in time, then so be it; you better bring some evidence to back up those claims, though.
Absolutely not. This is not fair whatsoever because the sheer absurdity of the so-called "graph" is off the charts, no pun intended. To blame a religion for a lack of scientific development is like blaming Communism for creating Joseph Stalin. Communism isn't inherently bad; some of the people that have held that political affiliation, however, have been. Basically, don't blame the ideologies for being poorly conveyed by its followers; blame the followers for misrepresenting their ideologies. Christianity didn't cause that scientific stagnancy, the people did.
The Dark Ages were caused by the decline and eventual fall of the Roman Empire in the 6th Century AD. With the most powerful and advanced empire that had ever existed at the time disappearing from the map, science, religion, and the arts all stalled up. People began to regress back into more simplistic lifestyles, such as a farmer or peasant. Quickly thereafter, education diminished into near non-existence. Some of the richer, higher classes still received mediocre academic teaching, however it wasn't sufficient enough to provide Europe with enough intellectual, inquisitive minds to further the sciences of the time.
That vicious cycle ravaged all of Europe (and parts of Asia), not allowing for many scientific gains to be made. Although the Dark Ages weren't really all that "dark" - it was more of a period of progressive dormancy - it was definitely a significant time in European history during the Middle Ages. Christianity became popular during this period because of two reasons:
1. The Church forced its beliefs on many people from many different cultures through fear and the threat of eternal Damnation.
2. Without science or education to inform people on why certain phenomenon occurs, supernatural activity was naturally assumed.
Now, neither of these reasons are grounds for blaming Christianity mainly because the religion didn't hold back the sciences - a lack of order, education, and intelligent minds did. Yes, it can be argued that because of the Church calling most of the scientific gains that were beginning to be made heresy was a hindrance on the scientific community, however remember that fundamentally, the Christian faith does not condemn the sciences that the Church did. The people are why those hindrances occurred, not the religion.
Science attempts to study how and why NATURAL PHENOMENON occurs.
Religion attempts to study how and why SUPERNATURAL PHENOMENON occurs.
They are NOT contradictory. (This, of course, excludes most Fundamentalists.)
Like I said in the beginning of this post, blaming a religion for the actions of its followers is like blaming a political stance for the actions of its affiliates. Just because the Christians were stupid asses, that doesn't mean Christianity was one big wart on the backside of humanity. With that being said, I can confidently say that the "graph" above is a complete fallacy. The y-axis isn't even a logical form of measurement.
Next time, judge people on their actions, NOT on their beliefs. Someone can believe murder is wrong, then go kill an innocent person. The same concept applies to people that act a certain way in spite of their religious, political, or philosophical beliefs.
"I like your Christ. I do not like your Christians. Your Christians are so unlike your Christ." ~ Mahatma Gandhi