Martov and Lenin were part of one of the first marxist group in Russia. Lenin valued this very much, look at his letters about it for example around the first split. And another fun fact about it: when filling in the obligatory party documents, to the question “Since when you are in the party?”, Lenin till the end of his life always wrote “1893 (party founded in 1898)”

Martov himself was also one of the main editors of the original Iskra, along with Plekhanov and Lenin (there were few more people but those three were the mainstay and wrote the most), and he would very much liked to remain comrades. Even during the WW1, after years of conflict, he still tried to reconcile on a base that Martov was among the internationalist mensheviks. Just as during the reaction times he tried to reconcile with Plekhanov on a base of the latter not joining the liquidators. In both cases it was ultimately impossible, but it’s not the fault of Lenin.

And here come another part of liberal smearing of Lenin, that he sacrificed personal relations on the altar of politics. Which is incredibly idealist and individualst concept, especially that Lenin’s friendship with Plekhanov and Martov was organized around their political activity.