The simplified explanation is this: the target of the attack by the group is no longer a person, but merely a target. Group members demonstrate their loyalty to the group by gradually escalating the violence they do to the target.
The principles and techniques can be very effective, but it depends on what/how you train (or who you train with).
There are many reasons to train, and based on your reasons, you should choose the martial art you wish to study, and also the teacher/school where to study. That said, it can be a great idea to study with a good teacher (but of an art you are less keen on) who is close by, than the perfect martial art which you can only get to infrequently.
Aikido isn't the best art to quickly learn how to defend yourself if that's all you want to do. But it has many pluses - "old man's judo" as a friend of mine said - you can keep going and keep getting better (if you practice) inspite of age...
I can recommend: https://www.amazon.co.uk/Meditations-Violence-Comparison-Mar... for some thought provoking reading and study.
I am not sure Maslow is saying what you think he is saying, since after all he grew up in Brooklyn. :-)
I would suggest reading Meditations on Violence, which is a beautifully flawed book, including a great section outlining a theory of violence, and what precipitates different types of violent behavior.
It's not a book about fighting. It's about how your bodies mental and physical senses react to violent situations.
Even if you've never been in a violent encounter, this book will help you understand how you will react. Keep in mind, you don't choose when you become part of a violent situation, violence chooses you.
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