i think it's important to understand Protecting Activity of Mahakala, that it is about protecting inner values & dharma teachings, and not about violence toward living beings.
i've tried to translate & paraphrase Buddha Karmapa 17th Trinley Thaye Dorje's words written in Polish language, to my best ability - for any faults, i apologize.
Who are protectors?
In the West, according to our tendency to perceive phenomena in a dualistic manner, we see them as something outside. Are protectors a kind of beings?
Protectors are our wisdom's nature. It's not about that we are here, and protectors 'somewhere', where they 'do something for us'. Awakening of our wisdom's nature is protection in itself.
There are two types of protectors: worldly living beings, and Dharma protectors, being absolute wisdom.
Enlightened protectors are Buddha's wisdom aspects, as for example: Mahakala.
How protector's activity works?
Generally, activity of a worldly protector is protecting area, nation or place from troubles or harmful influences.
Most important activity of Dharma protectors is protecting teachings. Their main activity is not about external threas. Dharma protectors save us from 'inner enemies' - disturbing emotions as attachment, confusion, desire, anger and pride. Protectors help us to control these weaknesses. This way they wrap protection around those who practice.
Through Dharma protectors, as through other Buddha aspects, enlightenment expresses in it's three qualities: wisdom, power and compassion.
We all have Buddha nature, but to recognize it, we need proper conditions.
Protectors' tasks are creating these conditions for us - they protect us from situations hindering our development and help us to find best conditions for recognizing our inborn Buddha nature. In other words, these energies remove hindrances from our way to enlightenment.
How a buddhist can physically protect others or fight for his or her own nation?
When we talk about protecting nation or even planet, it's usually that we mean killing and wounding others. If we are wounding other being, especially when there's ego or anger, it's not Dharma activity or even a buddhist activity at all.
If someone was attacked and you witness this, of course - protect, it's a completely normal reaction, everyone would do this. But try to not wound, to not kill attacker. Even in very difficult situations it's possible to avoid killing. Taking life is something extreme.
May all beings have happines and causes of happiness,
May they be free from suffering and the cause of suffering,
May they always experience true happiness, which is totally free from suffering,
May they remain in the great equanimity, which is beyond attachment and aversion.
FIVE WISDOM BUDDHAS
OM MANI PEME HUNG
Namaste, as well.