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These hypotheticals all have one purpose, to show that those who claim to believe that life begins at conception do not really believe it. I like to challenge them on birthdays vs conception days for the same reason. They don't walk their own talk. They are like prohibitionists with their own stash of bootleg rum, or drug users supporting the war on (some) drugs, or closeted gays supporting homophobic laws.
They don't answer because there is no answer consistent with what they claim to believe.
I sometimes wonder how these people can live with themselves, saying one thing and acting otherwise. They have long since ceased to think.