The historian David Gibbon attributed the decline of the Roman empire to, in large part, the unwholesome influence of Christianity.
As the happiness of a future life is the great object of religion, we may hear without surprise or scandal that the introduction, or at least the abuse of Christianity, had some influence on the decline and fall of the Roman empire. The clergy successfully preached the doctrines of patience and pusillanimity; the active virtues of society were discouraged; and the last remains of military spirit were buried in the cloister: a large portion of public and private wealth was consecrated to the specious demands of charity and devotion; and the soldiers’ pay was lavished on the useless multitudes of both sexes who could only plead the merits of abstinence and chastity. Faith, zeal, curiosity, and more earthly passions of malice and ambition, kindled the flame of theological discord; the church, and even the state, were distracted by religious factions, whose conflicts were sometimes bloody and always implacable; the attention of the emperors was diverted from camps to synods; the Roman world was oppressed by a new species of tyranny; and the persecuted sects became the secret enemies of their country. Yet party-spirit, however pernicious or absurd, is a principle of union as well as of dissension. The bishops, from eighteen hundred pulpits, inculcated the duty of passive obedience to a lawful and orthodox sovereign; their frequent assemblies and perpetual correspondence maintained the communion of distant churches; and the benevolent temper of the Gospel was strengthened, though confirmed, by the spiritual alliance of the Catholics. The sacred indolence of the monks was devoutly embraced by a servile and effeminate age; but if superstition had not afforded a decent retreat, the same vices would have tempted the unworthy Romans to desert, from baser motives, the standard of the republic. Religious precepts are easily obeyed which indulge and sanctify the natural inclinations of their votaries; but the pure and genuine influence of Christianity may be traced in its beneficial, though imperfect, effects on the barbarian proselytes of the North. If the decline of the Roman empire was hastened by the conversion of Constantine, his victorious religion broke the violence of the fall, and mollified the ferocious temper of the conquerors (chap. 38).
Not a bad thing to keep in mind as we reflect that 81% of evangelicals voted for you-know-who.