"You would be discouraging high-frequency trading, and this would definitely impede on their business model."
Why, out of all the problems on Wall Street do high frequency traders bother them so much. The flash crash had no affect whatsoever on the majority of buy and hold investors who simply ognored what happened on that day. Only people "hurt" were day traders willing to take on that risk anyway.
Also if they tax the transactions, the amount of trades will drop drastically so their forecast of tax revenue is wildly over inflated. Does anyone in Congress have a finance or intelligent background?