Actually I think you had it right the first time. The vague suggestion that somehow, maybe, possibly U.S. astronauts might travel on foreign or commercial manned launches (which do not yet exist) into orbit strikes me as spin meant to put a positive face on a very bad idea. This would effectively mean the end of NASA's manned space exploration program, but if you mention that, proponents of this half-baked plan can immediately counter with vague ideas - but no concrete plans - of how we might still participate in manned space flight.
Apollo or Delta manned launches aren't happening. I'm hardly that knowledgeable on the subject, but are there actually any safe, reliable commercial manned spacecraft (capable of reaching the ISS, at a minimum) far enough along in development that they could be ready before Ares, which has been in development for several years now and indeed already had a test launch? If being over budget and behind schedule is cause for being canceled, then the Space Shuttle shouldn't have been built either, nor should most military weapons programs.
But there is a far more compelling reason to keep Ares in the budget. It's a U.S. spacecraft. What happened to pride in your country? I'm pleased to see the International Space Station nearing completion with U.S.-Russian cooperation, and when the Chinese land on the moon I'll be genuinely excited, but I really want to see the United States doing these things itself.
In the early 1970's we could land a man on the moon, and indeed one of the chief Apollo designer s Werner Von Braun wanted to "scale up" the technology to reach Mars back then. Forty years later, with the shuttle retirement, if Ares gets canceled the U.S. will have lost the capability to (at least independently) even put a man into orbit. That's so far beyond sad it needs a new word.