The first step of an abusive relationship: Take away their support network...
In the books, the International Statute of Wizarding Secrecy presumably has an exception for the immediate families of Muggle-born wizards. The families of Muggle-borns we meet in the books (Hermione, Lily) know plenty of stuff about magic. But outside of that, there's nothing. Worse, it's not common practice to tell Muggle-borns about their abilities before the year they enter Hogwarts. (And not from lack of ability to identify them earlier. All magical children are detected at birth.)
I'd be very surprised if there isn't a large achievement gap between Muggle-born and wizard-born students at Hogwarts and other schools. Muggle-borns are, at age 11, shoved into a new world they know nothing about, and to make it worse, they're not allowed to talk about it even with their closest friends.
Thus, even though the Statute doesn't have an explicit blood-purist ideology written into it, it's still designed from such a magical-world-centric point of view that it hurts the very people who are already hurt the most by prejudice and discrimination.
Does this remind you of anything from real life? Please answer in the comments!
(In the books, all the major characters who were raised by Muggles – Harry, Hermione, Lily, Tom Riddle – are quite successful at Hogwarts. This is consistent with the books' general pattern of ignoring the more insidious aspects of social injustice.)