Had this tazering happened at a Press Conference by President Bush there would have been hell all over. Committees from here to eternity, civil rights violations, New World order crap and so on.
I would imagine that the Secret Service officers protecting the President don't carry tasers, as they are too bulky and are not part of what I understand the Secret Service's mission and responsibilities to be. An equally belligerent and abusive reporter at a Presidential Press Conference would have been treated with considerably greater harshness, I'll wager.