There’s a lot of crossover. Many libertarians favor the war and a strong defense. In my precinct, the majority of Republicans and libertarians favor Life.
Winning elections in this country is about energizing the base, and building coalitions.
It could be surprisingly hard to build a coalition, if you hate some of your potential allies more than you dislike the political opposition.
I have an acquaintance who does, he tried to start a 'Neo-Libertarian' movement (in which I agree a lot with) that is strong defense Libertarians. In turn, he is completely trashed and booted from the Libertarian and Ron Paul movements. (it didn't help that he used to work directly for Paul but quit because he said Paul was anti-Semitic). The Libertarians as a party, nor the Paul people seem to want to compromise on their defense platform, so why should the people of whom this is a top priority issue, compromise for them?