Impertinence, or just responding to a very real threat of getting thrown out of the House by his constituents? Probably the latter.
I believe Conrad has a pretty formidable opponent this time around so he's pretty nervous.
Conrad lives in a conservative, coal producing, state. He has to act in accordance with the realities of the state he is in. He gains more support by going against Washington. Besides, the Countrywide mortgage scandal is knocking loudly at his door.