By not opposing you are supporting. If in front of you violence is going on and you say that you are not doing it and do nothing to stop the violence, you in turn are causing moral violence.
If a house next door is on fire. You come to know about it, but do nothing to stop it, rather keep playing carom board in your house, you are committing moral violence.
This is the most common violence prevailing today. People see injustice, corruption and violence prevailing all around them, but they have learnt to become indifferent to it. They say that they know that it is wrong, but alone what can they do.
“To mind one’s own business”, indifference, self-enclosure, self-centredness, selfishness, lack of sensibility, lack of communication, egoism, self-righteousness, etc. are fertile grounds for moral violence.
On the other hand, solidarity, compassion, communication, interest for those next to us, voluntary action for social benefit, participation in social affairs, etc. predispose people in the opposite sense.
To take a firm stand in life against injustice, inequality, discrimination or violence is to start to become an activist, to give meaning to our existence. Otherwise there is no difference between us and any animal say, a dog on road.