Ends and Means

"Desperate times call for desperate measures" .Agreed.But should this be a reason of preaching violence ? The means DO justify the ends in rare cases when your existence is threatened but can it ,ever, be an option even when you have democratic means available to make your voice heard ?
Montgomery(Read http://en.wikipedia.org/wiki/Montgomery_Bus_Boycott) was meant
to put pressure on Government of the day and U.K. declared war on Germany when it became clear that Fuhrer understands no language but force.
Today both Montgomery and R.A.F. fighters are hailed as heroes..