No, militant libertarianism is not an oxymoron. Libertarianism means freedom, it does not mean pacifism by any stretch of the imagination. I believe that measures up to and including violence should be used to force freedom upon the entire world. I do not believe alternatives to freedom should be considered, regardless of the number of people who support alternatives to freedom. Essentially, I believe that there should be totalitarian (in that no other systems should be open to consideration, anything other than libertarianism is slavery and unacceptable), violently enforced freedom. This is not contradictory in the slightest, a free person can voluntarily be the 'slave' of another but anyone who uses violence or the threat of violence to control an unwilling person who has not initiated force, should have violence returned against them until they are incapable of continuing their immoral force.