All anger arises from fear.
All fear is irrational but some fears go beyond the egoic sense of self.
The deep anger that arises from the fear of something pure or innocent being corrupted or defiled, can be harnessed.
What is it that is so important to you, that it causes such a visceral reaction within you?
Congratulations - you just found your deeper purpose, something worth expending your effort towards. Focus on protecting & nurturing the light that you found so pure & innocent.
Transmute the anger into purposeful action. Use that fire to drive your action. Focus on protecting & nurturing the light rather than the darkness that you think threatens it.