I agree with all you've said about Canonical and Ubuntu; they've built something that doesn't allow others to build further upon it, and in doing so they're hurting the community and hurting Free Software.

Rather than attempting to convince Canonical, though, I think the right message should be "don't build on Ubuntu, build on Debian". Canonical has made it abundantly clear that they don't want derivatives; meanwhile, Debian has made it clear that they do.