Asklemmy

If diverse opinions were allowed, what was the entire focus on eradicating factionalism?

The general line according to Stalin (e.g. in "Foundations of Leninism") was that there should be thorough and exhaustive debates among those with differing opinions within the Party but that, once a resolution was reached by a vote following the debate, further fighting on the topic as a Party official was essentially a form of wrecking, though of course matters were revisited periodically (for good and for ill). Even if you disagreed, you were then expected to go along with whatever the motion was in the interest of the integrity of the Party as an actor. This was "Diversity of opinion, unity of action" [edit: I got the motto slightly wrong, see cowbee]

I don't really have a developed opinion on it (I guess I should have left this to cowbee for that reason) but I definitely have sympathy for this approach when I look at it in the context of glory hounds like Trotsky being constantly contrarian for the sake of political brinkmanship instead of, you know, acting in good faith and believing in things besides that he should be top dog. There shouldn't be tolerance for people like that, and the long-term harm that Trotsky's opposition bloc did to the SU is hard to fathom.