To reinforce what redtea said, talk about ideas, concepts, try not to use communist jargon, just let the ideas speak for themselves. If your friend has heard any marxist terminology it has almost certainly been painted in a negative light, and they've probably been lied to about what it actually means.

Start by getting them onto the same page as you with caring about people and slowly but surely work with them to introduce ideas and terminology once they're in a better position to just not reject it out of hand. Don't ever try a "gotcha" moment where you reveal that you were secretly teaching them communist stuff, always stick to a "this is what I believe" or "don't you think these ideas are useful ones?" always keep it personal.

They might be able to reject some abstract spooky scary communism that Ben Shapiro told them killed a million billion people, but they can't reject their friends easily, especially if they agree with them, and if your friend has any empathy at all, they will agree with you, because communist ideas are about helping people.