How does a monk cope with all the bad things happening in the world if the only thing monks do is sitting and meditating?

Don't monks have any urge to be an activist against for example all the violence against animals and human rights where they can help other people for their needs. How do they deal with those feelings of injustice, how can they justify themselves not to declare or demonstrate or be active in other way to stop these cruel things if they have a heart for the world. How can they just sit and meditate in a monestary?