Bluesky, you might really like that Dan Millman book, which is the same one I referred to "Way of the Peaceful Warrior".
I guess my question would be, is it possible for a person to evolve to the spiritual stage and have a streak of violence, which could be transformed by a spiritual practice such as martial arts.
To address that question, astrologically there are so many possible paths depending on the karmic and evolutionary condition of a soul. For example, I know a soul who is in the spiritual state who has the sn in Aquarius in the 1st house, squaring Uranus in Scorpio in the 9th. Prior to this life he has trained extensively in martial arts- possibly with special roles to fulfill, traveling long distances, sneaking into places, doing spy work etc. In this lifetime, he knows how to fight. Strangers sense his energy and try to pick fights with him all the time. He has learned to use his martial knowledge only when absolutely neccesary. He does not ever want to be violent towards anyone. He is currently in a committed relationship and raising a family. So in this case he has learned to transmute his anger by way of opening his heart to being a householder, being a partner, and letting go of the solo path.
On the flip side-
I just counseled a soul who has Pluto in Libra in the 10th, NN in Scorpio in the 1st, with Neptune in Sag in the 1st (not conjunct) which squares Neptune in Virgo in the 9th. What did I recommend to her? That she explore intensely rigorous physical activities such as Kundalini yoga, and or martial arts. She has one hell of a lot of suppressed anger and a karmic pattern of self destruction/masochism.
Martial arts would be a very appropriate spiritual practice for her, which in this case would help her learn how to be defensive in a way that is natural and necessary. This would allow enable her to become more responsive and active in pursuing her own dharma, on her own.