Your opinion that life begins at conception is just that, an opinion. I know you think it is proven beyond a doubt, but that is just your interpretation.
Well, yours and a lot of other peoples' as well, but it still is a point of view, most generally based on religious convictions.
If my opinion is that animal life is equivalent to human life (crazy, sure, but a lot of people do believe this. Stay with me) and that eating meat is equivalent to murder, since an innocent life has to be sacrificed for the meat we eat, is it OK for me to impose that opinion on the rest of society by force of law? Should I be able to impose a vegan diet on the whole country because of my belief?