Being able to stand up for your beliefs or a particular cause takes courage. It's a learned attribute, not an inherent human characteristic. It's not necessary to feel strongly about every issue, but what does matter is that some things do matter. Be vocal about what you believe. But remember to listen, particularly to those who disagree with you.
Enthusiasm is contagious.
Tell and show others why what matters to you does. Chances are, your passion will entice them to live with a sense of conviction, too. You don't have to change the world by yourself. Join an organization that supports your beliefs and work toward your goals with a whole team. Take a risk.