When you say it like that it sounds it is bad to be biased in this particular situation.

First of all it sounds much better than "I read it, he is correct. This is why I wrote mine." considering that he is refuting the idea presented.

Being biased is simply being opinionated and luckily Zed Shaw's opinion is that everyone should/can learn code. This is why he has free books, which actually teach some programming to everyone.

The thing being argued here isn't whether Jeff or Zed is right, the thing being argued is that Zed Shaw grossly misinterpreted what Jeff was saying, which he did.