Clashing values
Forget the ‘stand up for what you believe in’ bullshit. Acknowledge that people hold different values and it doesn’t make them evil. Express what’s making you uncomfortable in a values-neutral way. Communicate in a way that makes others, especially your boss, willing to understand your dilemma. Don’t do this, if your boss is a "do-it-because-I-said-so" type (run instead). Look for alternative solutions, avoid putting the other person down. Embrace diversity despite its side effect of bumping into disagreements along values lines.