Here is the text of an email I sent to the President of the ACM, Alain Chesnais (firstname.lastname@example.org) and the director of the ACM’s lobby effort, Cameron Wilson (email@example.com). For more context, there is a good article in the Guardian.
I am writing to express my concern that the ACM is tacitly supporting the Research Works Act. I have read the blog post  of M. Chesnais, the ACM president, and to me it reads much like he is an ostrich putting its head in the sand. This act (and others like SOPA) will have major negative implications for research in the computer science disciplines.
That the ACM is international, or that the President is not American, is immaterial. Elsevier is likewise ‘international’, and that has not stopped it from making major financial efforts to influence this legislation. The reality is that US policy and the US market is so important that it has international significance.
I would like the ACM and its affiliates to publicly disavow the Association of American Publishers by cancelling membership. I would also like a public statement to the effect that the provisions of the RWA are anti-science and anti-progress – in short, contravene (at least) Article 2 of the Constitution, which states the ACM’s purpose is to foster the “open interchange of information”.
This issue is so important that neutrality is not acceptable.