Admit it. When the chips are down, and it really would matter, nobody ACTUALLY thinks a fertilized egg is a person or would treat it as such.
You're wrong, here's one person who believes life begins at conception. If a newborn baby is a human, why not a baby just before birth? If a baby just before birth, why not a baby a week before birth? If a baby a week before birth, why not a month before birth? If a baby a month before birth? Why not six months before birth? If a baby six months before birth, why not a baby eight months and three weeks before birth? If a baby eight months and three weeks before birth, why not a baby at conception?
Each step back in time brings us to a baby that, if we are to define it as not human, we must appeal to some arbitrary criteria, in the same way that we somewhat-but-not-entirely arbitrarily decide that 16 is old enough to drive, 18 is old enough to vote, 21 is old enough to drink, 25 is old enough to run for Congress, etc.
But unlike the denial of these other rights based on age, mental, social, and physical development, if one is denied the basic right to life before birth, one cannot enjoy it later. Life removed is life irrevocably removed.
As absurd as you find it to regard a (temporarily) microscopic organism as a human organism deserving of the basic right to life, you must understand that your sense of absurdity is a cultural bias, it is not an argument that an unborn baby (at any stage of development) isn't a human. Either now or in the past there existed cultures that would have thought it absurd to value the life of a woman or child or newborn or person outside the nation/tribe/ethnicity/race as equal to a man. How big, how fully grown, or how fragile or self-supporting a human organism is is not an indicator of how human it is. If anything, the smallest, most fragile and defenseless humans are most deserving of protection.