Why do I refer to your statement as a red herring? Because you are ignoring the fact that supporting OOXML doesn't just allow users to have some interaction with the propriatairy MS format it also validates it as being relevant. And you are doing not only your users but the rest of the world a disservice with that.
You assume that since its an MS standard, it will be successful, and by supporting their work you are actually helping to make that a reality.
Actually, the millions of users with documents in that format validate that it is relevant. The market demand for inter-operability with the format validates it as relevant. AbiWord or some other program supporting the format only confirms that *other people* have deemed it relevant. That's how markets work. These "other people" are your potential users.
If one grudgingly supports OOXML *the format*, in the interests of allowing users to inter-operate with Microsoft-using colleagues, one need not approve of MS' actions during the "standardization" process or their (you say) lousy "standard". We don't approve of their actions. At all. We do support Jody Goldberg's attempts to extract better documentation from Microsoft. It makes life that much more difficult for them, while making our implementation that much easier.
Because we do this, doesn't mean that we don't whole-heartedly support ODF. In your attempt to show a "red herring", you set up a false dichotomy. (In fact, AbiWord is shipping on the OLPC XO machines with ODF as the default file format, and we're pleased as punch about that.)
Differing, redundant file formats drive market fragmentation and promote vendor lock-in, and should thus be considered evil, especially when they are proprietary formats. However, sticking our heads in the sand and pretending that Microsoft's OOXML won't get significant user uptake is (IMO) an absurd position. The pile of OOXML documents in my wife's inbox are proof enough that it already has. In this case, OOXML's success is measured by how much the community at large uses the file format, not how much you, as a potential implementer and free software enthusiast, like Microsoft, their actions during the standardization process, or their file format.
Disagree with the bad technical aspects of the OOXML format. Disagree with how Microsoft conducted themselves during the ISO standardization process. Shout it from the rooftops, all the while wholly supporting and promoting existing, open standards, such as ODF. I think that we're in total agreement on these positions.
But not (grudgingly) supporting the OOXML format hurts your potential users and your quest for openness more than it hurts Microsoft, at least at this point in time. Supporting OOXML allows your products to compete with Microsoft on ease of use, or preferred platform, or etc. It allows your would-be users to transition off of proprietary Microsoft products, platforms and "standards" and onto free-er products, platforms and standards. Like KOffice, GNU/Linux and ODF.
In your role as core KOffice developer, if you truly believed your own arguments, you'd remove the binary Excel, Word, Visio, and PowerPoint filters from KOffice. But I imagine that would be both politically impracticable and counter-productive to your cause.
We support our users and openness. If that means being able to inter-operate with proprietary formats, that's a choice that I'm comfortable making. But in no way should it be construed as our supporting Microsoft so much as supporting our users. To that end, I sincerely believe that being able to (at minimum) read OOXML files promotes those goals and is wholly consistent with software and personal freedom.