I followed up with a post about parents being the best teachers. Kids learn more from their parents about life attitudes then they do from their teachers, except in rare cases. Rohanna, you are assuming that those of us who are pro-homeschool believe that every parent is wonderful and good. I don't believe we are.
I work in public school. I'm a substitute teacher, so I see a different class every day, different age group, different school. And I see the difference of kids whose parents are "teachers" and whose parents don't give a flying horse hockey puck about teaching their children. The kids whose parents teach them are the ones that are engaged. Their parents at least pay attention when their kids ask them homework questions. They listen to read-alouds in younger grades, talk about things of academic interest (news, family history, things they remember from school that aren't complaints about how much they hated it). If they can't volunteer with the school or know nothing about the subject at hand, it doesn't matter, because they are modelling for their child that they take an interest in that child's education. With the younger grades, you can tell that these kids are the ones that you're going to see in Advanced Classes later on for the most part. For the kids who have learning disabilities and engaged parents, you can still tell, because the kid is bright and happy and eager to come to school.
The kids whose parents are not engaged are sulky. They act up in class. They designate everything "stupid" or a "waste of time". I see a young man who works in Alt Ed, and he tells me almost none of the students he meets have anything academically wrong with them, they just don't care. They have decided that education is a waste, because they were taught by their parents that education is a waste. They don't read anything more challenging than Cosmo or Sports Illustrated, and then spend most of class watching Youtube. If you ask what they want to do, if they don't respond model or sports star, they will flat out tell you they're going to have a bunch of kids and get a big welfare check so they don't have to work "because work is for suckers". Why not? Parents are the first teachers you have, and that's what they've been taught. They will teach it to their own children and continue perpetuating the cycle of ignorance and poverty, except for the odd one who decides that ignorance and poverty is the sucker's game and makes something of themselves.
There is no denying that parents are the first teachers you have, unless you have some guardian other than your parents. You spend more time around your parents than your teachers, and even the best teacher can't know a child the same way their parents can. That's why every parent owes it to their child to be an amazing teacher and role model, even if they are not a good academic teacher or would be terrible at homeschooling. But it is not fair to public school teachers or children to send off a child and say "I made this child, now you raise it for me. You be the teacher and the parent."
That's all the pro-homeschoolers are trying to get across - parents are the best teachers of attitudes, behaviors, habits, prejudices, and opinions. Even if homeschool is a bad fit for your child, you are still going to teach your child before they ever set foot outside your house. You owe it to them to teach them good things, and it's a crying shame that some people do not, since their children are the ones that suffer for it.