After seeing the discussion referenced here and on other news sites I skimmed through the Userlinux mail archive. Like most such debates where people feel something close to their heart is threatened the arguments where heated and anything that possible could be taken as a sign in their favour where not only mentioned, but brought forth as final evidence to where the world was going. Personally I doubt the exclusion from Userlinux in itself means that much to the KDE hackers; it will probably just be one of many smallish Debian based desktop distro's out there, and as was pointed out in the threads some of which are KDE based. My guess is that the reason so many of them has gotten so riled out about it is due the the many important edorsements GNOME has gotten lately, which I guess makes many KDE supporters fear that KDE is getting decoupled in the charge towards the corporate desktop. The Userlinux decision was probably just the drop that many them explode.
That said these decisions tend to synergize themselves. Userlinux is meant to be a Linux desktop solution and with Red Hat, Novell, IBM, Sun and their partners pushing GNOME as their Linux desktop solution then it is natural for a project with the stated aims of Userlinux to hook into that wave. If the stated goal is to attract a large number of ISV's to the Linux desktop plattform then the decision of vendors to close ranks behind the GTK+ API's is the best decision to achieve such a thing. Any other decision would be to replay the old divided Unix desktop scenario. And we all know how successfull CDE and OpenWindows where at attracting ISV's :)