Wikipedia doesn't claim to be unbiased, but rather that the information it supplies is not (Usually) biased, as it is user-contributed by various people of differing viewpoints. And Wikipedia should be biased
as a site, as it will be directly and adversely affected.
To take your examply of Walt Disney:
Walt Disney, a company that is heavly hurt by internet piracy, would be criticized for using their "nonbias" news networks to promote a law that benefits them.
This is true. But it isn't a parallel case; for Wikipedia to be compared to this theoretical case they would have to alter the information on their site (the wiki entries) in order to support their view. This they have not done. They have merely put forward their view in an article, raised awareness of the issue and made it clear that they could not function under the legislation.
None of this, in my opinion, makes wikipedia a biased or invalidated source of information. Nor is it, in my opinion, wrong. After all, Wikipedia is meant to help people; they make no profit, nor do they endorse piracy, so why should they be shut down? Personally, I feel that if legislation damages an innocent site like Wikipedia there is a problem with it.