Someone else could, yes. Or they might not. It gives society more of a chance that way, anyway. And I don't know where you got these ideas, but you're quite mistaken. Muggles aren't a part of our society at all. If you are proposing the radical step of repealing the international secrecy laws, that's another debate altogether, but it has very little to do with this.
Anti-muggle sentiment peaked when I was a small girl, you know, because of the Great War, which was their own doing. So long as they cause no harm to us, we're quite content to let them live as they wish. And muggleborns are just...quite necessary. If they attend school and learn about our culture, there is no reason they shouldn't have a place in the wizarding world. Who else is going to do all those dull low-level Ministry jobs?
I think that perhaps you know a few terrible, violent, prejudiced pureblood individuals, and it has made you think we are all that way, or nearly all?
It's quite alright. It's - well, my family didn't want me to involve myself at all. I did what I could, but it was never enough. It's how things are, I suppose. But anyone who has seen one war will not want another.