You can also point out the contradiction that they don't seem to be in a hurry to take the obvious first step by killing themselves. Proving that they see at least one human life as a net positive. Then talk about everyone else they don't want to kill or prevent being born.
Be aware, though, that this isn't truth-seeking. It's debate for the fun of it.
I think there's also a near/far thing going on. I can't find it now, but somewhere in the rationalist diaspora someone discussed a study showing that people will donate more to help a smaller number of injured birds. That's one reason why charity adds focus on 1 person or family's story, rather than faceless statistics.
Combining this with what you pointed out, maybe a fun place to take the discussion would be to suggest that we start with a specific one of our friends. "Exactly. Let's start with Bob. Alice next, then you. I'll volunteer to go last. Af...
If it's worth saying, but not worth its own post, then it goes here.
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