If we could just clarify exactly why birth control pills work, perhaps we could end this silly discussion. The premise of hormonal birth control pills is that they make your body believe it is already pregnant. When a woman is pregnant, she does not release any more eggs. Also, mucus thickens sp that no other sperm can get through. The point is that your body would not want to have two different pregnancies at different stages going on at the same time. That is how the pill works -- if your body thinks it is already pregnant, it will not allow another egg to be fertilised and implanted.
If you personally believe that any fertilised egg constitutes a pregnancy (whether that is in a dish in the lab or in your body or flushed down the toilet because it did not implant), that is your opinion. Your body, however, says no -- it is not a pregnancy, since it it refusing to acknowledge it.