The goalposts have moved a lot from the original argument, but the only way that you can make an argument about tolerance within the historical record is simply

The goalposts have moved a lot from the original argument, but the only way that you can make an argument about tolerance within the historical record is simply by ignoring intolerance to Jews, Persians, Christians (generally all non-Italians) and the various barbarians that Rome contended with. In fact, the intolerance of Germans and migrants, in particular, by both "pagan" and "Christian" (neither label really fits), was a key reason for the eventual fall of the empire. That was not necessarily religious, but arguing that the martyrdom period, as well as the German wars, were somehow more religiously tolerant the late empire, is ... dubious in my point of view. You can make arguments that the Middle Ages crusading church (i.e., the Catholic Christendom church 500 years later) was less tolerant, but few things in the Middle or late Roman empire (or anywhere in the world) could ever be described as tolerant.