From the chapter “Language, Truth and Logic,” in Lenin, a biography by Victor Sebestyen, Lenin’s debating technique before the revolution:
Those who disagreed with him were ‘scoundrels’, ‘philistines’, ‘cretins’, ‘filthy scum’, ‘whores’, ‘class traitors’, ‘silly old maids’, ‘windbags’ (one of his favourite epithets found frequently in his writings) and ‘blockheads’. Often he would resort to the obscene, in language rarely used in the St Petersburg society of that era — his opponents were invariably ‘shit’ or ‘cunts’…’He does not reply to an opponent,’ recalled Moishe Olgin, a long-time comrade who saw [Lenin] operate from the early days as a young revolutionary making his way in the Russian capital. ‘He vivisects him…’
…
…[I]t was his aggression and menace in debate that most struck his friends and foes. One of his intimates for many years was the highly sophisticated, clever and witty Yuli Martov, to whom for a while [Lenin] was probably closer than any other man…They fell out spectacularly over politics and became bitter enemies. In 1917, shortly before the Bolshevik Revolution, Martov was asked whether, even as an acknowledged atheist, he thought there might after all be life after death. ‘Oh I hope not. In my opinion one earthly existence is more than enough; do you think it would be fun to continue arguing with Lenin even after death and in the hereafter listening to his gutter abuse?’
Not a nice man, Comrade Lenin.