Laudator Temporis Acti

Charles W. Hedrick Jr., History and Silence: Purge and Rehabilitation of Memory in Late Antiquity (Austin: University of Texas Press, 2000), p. 47, with note on p. 268:

Paganism was by its very nature agglutinative, inclusive: there is no inherent reason why the god of the Christians should not have been worshiped along with Zeus and Mars. From a pagan perspective Christianity might be regarded as just another oriental cult, like that of Mithra or the Magna Mater—and many such flourished side by side in late antique Rome. So the leading characteristic of paganism could be considered its religious tolerance. Christians, on the other hand, regarded their god as preemptive: one could not be a Christian and worship other gods. The dichotomy of pagan versus Christian is a characteristically Christian opposition, as it is the distinguishing characteristic of Christianity to make exclusionary religious distinctions.³⁴

34. This argument is made in O'Donnell 1979b.

The reference is to James J. O'Donnell, "The Demise of Paganism," Traditio 35 (1979) 45–88. See e.g. O'Donnell, p. 52:

In summary, it is necessary to look upon the religious sociology of the fourth century with two separate (if often, and confusingly, overlapping) distinctions in mind: that between worshippers of Christ and worshippers of other gods; and that between men who could accept a plurality of worships and those who insisted on the validity of a single form of religious experience to the exclusion of all others.