I have been in battle with people over values and principles. What I have learned is that I need to be selective about the battles I fight. For certain people, to battle them constantly is inconsequential no matter how much truth you present. Sometimes we need to conserve our energy and use it on more productive endeavour.
Discussions are always better than arguments because an argument is to find out WHO is right, and a discussion is to find WHAT is right. Learn to discuss reasonably and righteously. Those who do not have this capacity would only raise their voices and increase their arguments rather than to humbly and honestly look at the issues and improve their discussions. To take them on is an exercise in futility. Keep calm. Focus on the issues and treat it with truth.