Do you have any religious friends?

A few, but the "religious" here in France are milder than what you'd get in the states. The most religious people I know are Muslim.

If they're educated they'll point to examples of people who justified atrocities with "the ends justifies the means." (ex, Mao's Great Leap Forward)

That's a very reasonable answer! "The end justifies the means" is a common rationalization for terrible behavior (though probably not as much as it is in fiction).

• A) Someone with a high earning job should donate money to charity instead of volunteering.
• B) The only reason I shouldn't rob a bank and the money to an efficient charity is because doing so will decrease net utility in the world.
• C) By diverting money from more efficient charities, the Make-A-Wish foundation does more harm than good.

Thanks for the examples, these make sense, though they seem somewhat tame (I would expect stronger disagreement and conflict over issues like how to raise kids, abortion, dealing with crime, race, globalization, immigration, taxes, nuclear power, the rich/poor divide, divorce, etc.)

But then, I don't go around telling people "I'm a utilitarian" anyway - unlike atheism, I don't see how it would come up in normal conversation (i.e. if someone disagrees with me about the relative merits of donations and volunteering, I don't expect them to say "but that means ... you're a Utilitarian!").