While I don't have any particular reason to oppose homeschooling or unschooling, as some of the smartest people I've encountered were homeschooled (haven't met any unschoolers yet), I would like to speak up in defense of my particular experience in public school (who knows -- maybe it will add a little bit of variety to this topic!). My parents taught me to read at the age of two and packed me off to public school, and I did just fine. I tend to enjoy more institutionalized settings for learning foreign languages and math and science. I did hate my history and government classes, but I was able to laugh about them with my mom and dad at home.
In many cases, I don't think it's purposeful indoctrination so much as not being able to tell the entire story due to time constraints. Teachers aren't always evil automatons concerned with only teaching one version of something; typically, if I debated with them in a friendly and respectful way, they would respect my interest in the subject. There's a way to disagree with something without coming off as disrespectful. My American History I teacher in particular was able to present the Civil War in a very balanced fashion, and even got into the deeper, economic root causes of the war. A lot of libertarians like to caricature public education for, I suspect, dramatic effect, but these caricatures don't always approach reality. That being said, I am quite aware that there are a lot of issues with other public schools. I was fortunate enough to go to one of the top school districts in my state.
I guess I am playing devil's advocate here because I don't like hysteria coming from either side in regard to this issue. Kids that haven't been raised properly at home being made to go to school (or perhaps any other institutionalized setting) is a toxic scenario; I am seeing the proof of this statement with my cousin's daughter now, who just had to be enrolled in cyber school -- I certainly wouldn't trust my cousin to homeschool her children.