This analysis seems very confused to me. I believe there is great value in traditions and cultural belonging. I also believe there is great value in critical thinking. A culture based on traditions, with people who never questioned those traditions, is dead because it has no foundation.
I cannot be proud of "my country" if this is based on keeping me from thinking critically. I can be proud of the fact that people who wanted to make their world a better place, or keep parts of their world a good place, are valued in the society I live in.
There very essence to "indoctrinate children", as you call it, would be to tell them to stop dreaming of a better world, but be quiet and be proud of what is. Any society of that kind has either died, because it is unable to adapt to new challenges, or turned into a violent, totalitarian and suppressive system before collapsing.
Branding the works of Howard Zinn as "indoctrinating" is utterly absurd.