Why did the Roman government view Christians as enemies of the empire?

Christians were not really viewed as enemies, but they incurred the displeasure of the pagan Roman government because they did not seem entirely loyal. The emperors were concerned that Christians could not be relied upon to do what the government required, preferring to accept the authority of their own bishops instead, and thus fostering disunity in the empire. Nevertheless, the government generally preferred to ignore the Christians, and there were really only two brief periods of official persecution - 249 to 251, and 303 to 311.