When politicians seem to act in a confusing and contradictory manner, then maybe you don't understand their objectives.
For example, back in the 1980s, US foreign policy confused me. I thought it was supposed to secure liberty and democracy at home, by supporting and defending them abroad. So the coddling of rightwing dictators made no sense to me. Instead of containing Communism, US foreign policy was actually creating the conditions that fomented revolution.
When I finally learned the real objectives of US foreign policy, I was no longer confused:
No matter which party is in power, the U.S. acts to protect the interests of large American-based corporations, in order to maintain valuable overseas markets and cheap foreign labor.
When I viewed US foreign policy from that cynical viewpoint, it became much more coherent to me.
So to understand the actions of the Democratic Leadership, we have to forget about the "frivolities" of upholding the Constitution and International Law. We have to maintain a cynical viewpoint and consider their real objectives.
How many times have you heard that the first "duty" of a politician (or a political party) is to win elections?
When it comes to gaining and holding power, the Republicans have demonstrated (on numerous occasions) that all other considerations are secondary. Why should we assume that Republicans hold a monopoly on this cynicism?
The Democrats have no real interest in deterring future Republican abuses, because those very same abuses have produced a huge Democratic victory. Once you realize that, then you can understand why the Democrats will not be punishing Bush Administration criminals.
If the criminals in the Bush Administration were punished, then that would help restore a respect for the rule of law; future Republican Administrations would be less likely to abuse their power. But where is the Democratic electoral advantage in that?
Rather than restoring a system of Constitutional government that forces future Republican Administrations to behave, the Democratic Party is giving us only one means of preventing future abuses: by keeping the Democrats in power.
When you look at the actions of the Democratic leadership from this point of view, then their "failure" to stand up to Republican extremism makes a kind of sense.
Look at how many times the Democratic leadership has capitulated in the face of Republican extremism and abuses. These senseless capitulations became so commonplace, that we began making jokes about the Democrats' "dry powder" and their use of "sternly worded letters". The resulting Republican mismanagement gave the Democratic Party an election victory, the likes of which we haven't seen since 1932.