Look, I genuinely don't like arguments which start "Well, a Grand Old Beard said...", but your question sort of presupposes that sort of response, so forgive me in advance.
The parties led by Lenin and Trotsky all contained ideological differences within their ranks. In fact, they contained rather wider disagreements than the Socialist Party does. The notion that the party must be politically homogenous and must not tolerate dissent outside the ranks and/or must not tolerate organised internal dissent is something that stems from the 1921 ban on factions and then further innovations by, amongst others, Zinoviev and then Stalin.