The south were so entrenched in slavery they fought a war that there was never any real hope in hell they could have won to preserve it.

There are and were only two options. 1. Someone kills enough of them to stop them treating human beings as objects to be owned or 2. You let them carry on doing slavery in which case there'd still be slave auctions in the south today. Those are the only two choices.

I'm not a general or whatever so maybe there was stuff tacitcally or strategically John Brown got wrong but the general idea of murdering and terrorizing slaveowners was absolutely the correct and 100% morally justified decision.