Frank McLynn is definitely on the side of the thesis that Marcus Aurelius was a persecutor of the Christians. He also believes strongly that the Antonine plague devastated the Roman Empire on an unprecedented scale (10 - 18 million dead from a total population of 60 - 70 million).
It is interesting to me that McLynn fails to link the two phenomenon. While he blames Marcus Aurelius for ordering the persecution of the Christians, I think he does not consider the possibility that the persecutions might in fact have been driven by localized "moral panics" caused by the plague. The ancient Greco-Roman pagans tended to ascribe natural disasters such as pandemics to the wrath of the gods, and it is certainly conceivable that the populace panicked that the Christians had brought down the gods' anger onto the Empire with their "atheism" (i.e.: disbelief in the traditional polytheistic pantheon of Greece and Rome and their refusal to take any part in the traditional religious rituals, particularly sacrifice). This might explain the disjointed and haphazard, but still numerous, incidents of persecution of the Christians during Marcus Aurelius' reign. Marcus himself may have been mostly unaware of the persecutions and been unable to do much about them regardless, since he was already busy fighting off barbarian invasions on the German frontier.
In the end, I think that Frank McLynn presents weak evidence that Marcus Aurelius really was a "committed" persecutor and enemy of the Christians. I think if far more likely that the Antonine plague was so devastating that local populations scapegoated the Christians and persecuted them on their own, rather than on orders or laws from the Emperor. Similar events occur over and over again throughout history, such as when the Jews were scapegoated and persecuted during the 14th century because they were believed to have created the bubonic plague (the "Black Death").
So, what to do you think? Do you find Frank McLynn's arguments that Marcus Aurelius was a dedicated enemy of the Christians convincing? Or, do you think that it was other factors such as the Antonine plague that caused the persecutions during his reign?