Rosenberg misses one thing - history. The tax increases scheduled for Jan 2011 are just the Bush tax cuts expiring. So we go back to the Clinton tax regime. Seems like the market did just fine under the Clinton tax regime. Furthermore, the market declined in the face of Bush`s tax cuts.
Of course there are a lot of other things going on, but there is no evidence to imply the market will go down simply because of the inevitable tax increases.