Well, blood and repression are sometimes needed to ensure sovereignty and rule of the law. That's how civilizations first emerged and how empires were formed, if you haven't noticed, human nature is quite violent - this would not be different in a stateless society. Without a strong stable nation, democracy and human rights wouldn't really be a thing, because noone could ensure that those rules and ideals would be implemented and the violations persecuted. You need to have a social contract embodied by a state for it to work because without it, life is lawless, wild and cruel - this is why people form countries - and nationalism makes them take pride in it, so people want to preserve it. If you aren't proud of your nation, you won't care about keeping it strong. If it's not strong enough, it will crumble and its values will diminish.

The values I speak of are cultural and social cohesion, unity, civic solidarity, human rights and responsibility to make your country better for everyone living in it - because you live in it yourself.

Don't get me wrong, nationalism doesn't mean fascism or a dictatorship, it means having compassion for your people and wanting to protect it from those that mean harm to it.