What does this quote about the Western Romans fall mean?

Oh, golly, Gibbons has a lot to answer for. He's a Victorian agnostic and his ideas are very much of his time. For him, Rome was great when it was a military empire and when Christianity became dominant and preached peace, the empire fell. Never mind, that Constantine won battles under the sign of the cross, never mind any of the economic problems of a huge empire with lots of enemies. Partly this is the old question we still have today: do you spend money on war or on taking care of the poor, sick, elderly (the demands of charity and devotion). Presumably your ignments will include some more recent scholarship.