Rome killed heretics, because Christianity was the state religion, and turned to the Church to speak to what is and is not Christianity. And the Church has condemned things like gnosticism as non-Christian from the very beginning. Don’t confuse Rome having an official prescribed acceptable set of religions with some nefarious scheme by the Church. It is the role of the bishops to speak to what the authentic Christian faith is; what the state - in this case, the Roman empire - does with that information, with regard to non-Christian faiths, is it’s own business. The Church is under no onus to accept false theology as Christian simply for fear that the Empire will persecute those people if they don’t. In fact, she would’ve been wrong to do so, and unfaithful to her commission by Christ had they compromised the Christian religion that way.
Rome killed heretics, because Christianity was the state religion, and turned to the Church to speak to what is and is not Christianity. And the Church has condemned things like gnosticism as non-Christian from the very beginning. Don’t confuse Rome having an official prescribed acceptable set of religions with some nefarious scheme by the Church. It is the role of the bishops to speak to what the authentic Christian faith is; what the state - in this case, the Roman empire - does with that information, with regard to non-Christian faiths, is it’s own business. The Church is under no onus to accept false theology as Christian simply for fear that the Empire will persecute those people if they don’t. In fact, she would’ve been wrong to do so, and unfaithful to her commission by Christ had they compromised the Christian religion that way.