Throughout the history of mankind there always were people, ideologies and organizations that used the phrase “The end justifies the means” as their motto or the leading principle. Its immediate meaning is as follows – if you have high, noble, important goal, you are free to resort to anything, however immoral it seems even to yourself. It may sound logical to some people – wouldn’t a just cause, usually restrained by its own moral limitations, be more effective if it borrows something from the repertoire of its enemies?
But another question here is: If it does so, in what fundamental way it will be different from these enemies? History shows rather clearly that any ideology speaking about building a better future, no matter what there is to be done in order to achieve it, if ever come to power, start moving towards this better future in a rather queer, yet very energetic way, which usually involved murdering as many people as possible in as many ways as it is imaginable. Hitler wanted to resurrect his country and lead it to world domination; Robespierre promised freedom, equality and brotherhood for everyone, Lenin offered land to the poor and so on. In the end, it always was bloodbath and nothing more.
When somebody says clearly that he is going to do everything to achieve the goal, it very rarely means that he is speaking about nice and pleasant methods; they do not require this proclamation.
Thus, the major rule is, I think, as follows: once you hear somebody saying “The end justifies the means”, either slap him across the face or run for your life.