For the same reason that I think it’s ok to interrupt other natural, life-producing processes. I ‘interrupt’ vegetables, cattle, pork, chicken, insects, bacterial infections, etc all the time. Interrupting life-producing processes is positively mundane, it’s that common. And let’s not play semantics, I’m not ‘interrupting’ anything. The fetus isn’t going to pick itself up thirty years down the track after the ‘interruption’ is over, and get back to having its life. It’s not interruption, it’s termination.
Might be relevant to you, but it isn’t to me. I see it as “kid could be here, if you want that to happen. If you don’t want that to happen, here’s one option”
Anyway, what’s this ‘should’ thing mean ? That’s a bit of a value-judgement, isn’t it ? Because Tab A was inserted into Slot B, #1 sperm reached egg and managed to fertilize it, and the egg successfully implanted, that means you need to become a parent ? Maybe in your world, but in mine, only those who want to become parents, ‘should’. See how value-laden that ‘should’ word is ?
Ummm. No. You’re killing a fetus. In my world, male does not equal someone’s dad, just as women does not equal someone’s mother. That fetus may have become a father, it may have become a rocket scientist, president, an abortion doctor, a child abuser, who knows ? My money would be on it becoming just an average ordinary Joe Blow, not anything special or horrible.
But if you are killing someone’s dad, shouldn’t we be figuring out the average number of kids everyone has, and then charging murderers with that number of deaths, in addition to the actual victims death, since they are in fact guilty of killing those future lives, too ?
Yes, I am. I don’t think I owe anyone a chance at life. If I thought that, I’d be permanently pregnant, otherwise how could I deny all those potential possible lives a chance at it ?
I have not seen the great rule book that states “you must do everything in your power to always give the chance of life to another human, no matter the circumstances”. If you find that book that details clearly how I should best live my life, please let me know. It better be free of contradiction, clearly written and fully justified, so there’s no misunderstandings on important points such as how to live my life 
Yes. I think I’m in a much better position to rule what’s best for my life than anyone else. I make many decisions, in fact I make all of them, when I can’t see into the future to ascertain the better option. I use my thoughts, opinions and feelings to determine the better option for me, and then move on, without crippling self-doubt on which option would be best.
I tried to answer honestly, but somehow I don’t think I’ll end up being very helpful. Oh well, I tried.