As you probably know already, I oppose the merger. Whether or not the merger goes through is another question.
However, after reading your post I came to disagree with a few of your points.
1. About Congress not having the power to stop the merger.
You are correct in saying Congress has no direct power, but were incorrect about the "foot stomping." Senator McCain is not looking out for the Phoenix-based America West, he is looking out for his constituents of Arizona and the people of the United States as a ranking member of the transportation committee. The same is true with the congressman from Washington.
2. The DOJ's approval of the merger.
The duty for the Dept. of Justice (as well as any other govt agency) is to look after the nation's people. As for reviewing mergers, they should look at the individual airlines. However, the review includes the possible effects of the merger on competition (hence the reason why they even review mergers). The possible effect of the UA/US merger inspiring other airlines to merge WILL play a role in the decision.
3. United's recent problems won't plague the merger.
I agree with you mostly on this point, but I believe that Rodney Slater and the DOT will not let this summer's "slip-up" pass on through.
The merger WILL decrease competition and can spur on higher fares and lower customer service. It's simple logic. Yes, (if it goes through) the merger would decrease the number of major airlines to 6, but what about AA/NW and DL/CO? Then we'd be down 3 conglomerates and TWA. The airlines do follow each other when they cut fares, but what about raising the fares? With fewer airlines, this would be very easy. Just take a look back in time about 120 years ago when railroads would merge and raise rates. Now, we have more laws to prevent enormous rate increases, but they wouldn't stop the "big 3." Also with a much larger UA, I don't see how the merger would improve service. The world's largest airline struggles enough as it is right now to provide good service and proper customer care (DOT and other reports).
I won't give you any grief about the 70/40 deal because we're only human and we all mess up
In response to IFLY767's post, yes United is bunch of airlines, but from what I've seen so far from the acquisitions, I'm not that impressed.
All in all, I hope and I think that the UA/US merger will not go through.