Interestingly enough, Christians were persecuted in Rome until a little after 300 A.D. and within less than a hundred years after adopting Christianity the empire split. The last emperor of the Western half of the empire was gone within 200 years of Rome’s conversion to Christianity. The Roman Republic enjoyed it’s greatest wealth and power long before Christianity even existed. I’m not at all arguing that Christianity brought down Rome. Rome had already gone way downhill by 300 A.D. It just ought to be noted that Rome’s greatest period was prior to the advent of Christianity.
Read "City of God" by St. Augustine of Hippo. He refutes the same thought some had in the 4th Century.