Yes, John Brown was a terrorist. His declared goal was to use violence, intimidation, theft, vandalism, and coercion against citizens who, rightly or wrongly, were abiding the law. Of course, this is just how his yankee financiers wanted it. Neither John Brown or the yankee financiers were willing to accept any reasonable diplomatic solution.
They could have made their case that slavery was morally reprehensible. They could have offered to purchase the slaves freedom. They rejected such options as outright.
John Brown raided Harper's Ferry hoping to start a slave insurrection. What would the only possible outcome of such an event if fully successful have been? All of the slaves participating would have been killed along with any whites caught helping them. Further something similar to pogroms would likely have occurred, and any attempt at ending slavery through legislation would have been delayed years into the future.
The yankees feigned their moral outrage when this low criminal was properly tried and hanged. Less than six months later that scoundrel Lincoln began the War of Northern Agression. Odd that during the Mexican War, Lincoln pronounced such wars to be unjust.
