You assume that "the movement behind Corbyn" is socialist, that this movement will somehow end capitalism without a revolution, and that the reason we support revolution is because we want "murderous violence". That's a lot of assumptions.

Corbyn is a member of, at best, a social democratic party. His supporters aren't interested in abolishing capitalism, and if they were, trying to vote capitalism out of existence is futile and comes from an idealist conception of how a change in modes of production actually works. The bourgeois state will not simply allow itself to be abolished. It will fight back, as it fights back against even the most milquetoast reformists (e.g., Sanders). And even if the bourgeoisie did, by some miracle, sit back and allow their peaceful downfall, to expect that downfall to happen through legislation passed by reformists is to literally expect the state to abolish itself, rather than for it to happen through class struggle. That is why a violent revolution will be necessary, not because we're just a bunch of bloodthirsty ideologues.