We've been working with the dart2js team to reduce the size and they have been making incremental improvements. AngularDart is smaller this week than last :-)
Both 170KB and 70.5KB are still pretty huge for trivial apps, though.
Take a look at the pull request queue on Github. We've been focused on 1.2. There are a lot of new features and proposals that we'll pick up now that the release is out the door.
It is also clear from the discussion that there are dissenting opinions -- we are constantly iterating and welcome issues and pull requests to make features work even better. The best way to influence AngularJS is to send a pull request.
The author is arguing against learning new languages / concepts by rewriting existing apps.
I'd argue that rewriting existing apps is a great way to learn a new language. By removing the app-specific learning, you can focus on the language. Even better, since you have two implementations of the same app, comparing language concepts is easy.