My family, friends, and colleagues know I speak out or act up when I see something I think is wrong. When asked why, my usual answer is that I was raised to examine and question things, to seek information, to make up my own mind, and to always behave in a way that is true to my values.
This explanation is true but incomplete, as it fails to convey my belief that silence is a form of acceptance and can be tantamount to endorsement. I offer an anecdote from my childhood as an illustration of what I mean.