Yes, I would. You don't have sex with your siblings, damn it. That is a line I draw and will not cross. I can't believe you're seriously arguing that there's nothing wrong with it.
YOU will not cross it because you are thinking of your siblings, siblings you grew up with, ergo you are already in this
http://en.wikipedia.org/wiki/Westermarck_effectHow do you know that you wouldn't find yourself experiencing the reverse,
http://en.wikipedia.org/wiki/Genetic_sexual_attraction if you suddenly met a sibling you had never known about, and never met?
You understand that most of these cases you are so disgusted by are stories about siblings who did not grow up together and never had that natural incest aversion that builds in siblings who live together?
Indeed some of the cases involve siblings who didn't even know they were related untilk after they started fucking and fell in love, and then society tells them 'sorry dudes, your related, you must break up now"
It's easy to judge from a position of so called normality.