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.
words like 'freedom' don't refer to anything or mean anything. you just have a desire for violence, glory, revolution, and all that fun stuff, militant 'libeterianism' is just an excuse to act out on these desires.... some people become fascists, marxists, etc., for the same reason. it's all puerile fantasy, and you'll grow out of it.
Freedom has a meaning, people who want to infringe the freedom of others claim it has no meaning though. I have no desire for violence, I have a desire for freedom and as libertarianism is freedom I have a desire for libertarianism. It would be far superior if libertarianism could be achieved without violence, however this is a fantasy that libertarians need to grow out of. Here is a small example of freedom
1. You can be a member of any religion you want, however you can not force your religious beliefs onto others or take actions in the name of your religion that infringe upon the freedoms of others
2. You do not have to pay taxes or for any service that you do not want
3. You can marry whoever you want, so long as they agree without being coerced
4. You can possess and obtain whatever information and/or other items you want, on your own land or land where it is permissible, without being restricted by laws (however you may be restricted by lack of resources, or by the freedom of others to set rules regarding the information/items that can be on land that they own)
5. You can consume any drugs you want, however if you are on land owned by another they may restrict which drugs you possess and what you may do under the influence of drugs while on their land (a person may own a street and forbid you to drive on it while intoxicated, conversely a person may own a street and allow intoxicated drivers)
6. You can own property on which you can set any rules you want that do not restrict another persons freedoms. For example, you can own land and say that weapons are not allowed on the land, this does not restrict another persons freedom to own guns it merely says that if they bring guns onto your land they are restricting your freedom to have rule over your own land. However, you can not say that people on your land can own slaves, as this would restrict the freedom of other people to not be enslaved.
7. You can say whatever you want and publish whatever you want, provided you do not say things or publish things that are against the rules on the property of someone else
8. You have freedom from being forced to work for another person against your will
Freedom is very well defined actually, if you want to know if something entails freedom or not see the libertarian position on it, if anarcho-libertarians are in favor of something it means that it is compatible with freedom, if they are against something it means that it goes against freedom.
Fascism and Marxism are completely incompatible with freedom. There is a major difference between militancy in the name of Fascism/Marxism and militancy in the name of Anarcho- Libertarianism: militancy in the name of the former ideologies is done to enslave people and militancy in the name of the latter ideology is done in order to free slaves.