DominusNovus said:
Well, it wasn't exactly that, as the Jews had official toleration, but Gentile Christians did not (Jewish Christians did), even though they both completely denied all other religions.
The Romans were great respecters of tradition. Judaism was one of the oldest religions ion existence as far as they knew (that, at least, was the claim made by its adherents), so of course it had to be tolerated. It wasn't that the idea of people 'believeing nonsense' would have caused the Romans to lose much sleep. They were happy to condone almost anything. THe problem with Christianity was
- it was new. There was no precedent for dealing with it.
- it was secretive. Nobody quite understood what was going on. There was predcedent for dealing wih that, and it was judicial and violent.
- it targeted Romans. Unlike Judaism, Christianity actively sought converts. THat was in itself not unusual, but combined with a prohibvition against the practice of any other cult, it was unsettling.
- it denied not only the status of other gods, it forbade their worship. It really wasn't too much of a problem to say Jupiter Optimus Maximus was 'just' a daimon, but refusing to take part in acts of divine worship cut you off from participation in all society. A rough approximation of the scope of the prohibition: imagine refusing to participate in any activity that involved money. Divine worship was part of Roman civilisation. The theatre, the races, the baths, the courts, elections, public festivals, civic affairs, military service, trade - there was nothing you could do if you did not make a token of worship. Imagine the disquiet a religion like that would cause today.
In retrospect it is amazing how calmly most Romans accepted thiese goings-on. Most places and times, Christians and pagans coexisted more or less peacefully. Until Theodosius, that is.