If you don't...
Your average congressperson knows very little beyond what lobbyists have paid to tell them. So if somebody were to tell them that the things they expect internet siteowners to do is so technologically impossible that the entire US Internet industry would be forced to shut down, you get little more than a blank stare.
Meanwhile, the large industrial concerns pushing SOPA and PIPA don't actually care what the repercussions of these sorts of bills are and it's doubtful that they've even vaguely thought this through.
The part that's just about as dangerous is sliding in new invasive Internet regulations that favor these large and staid industrial concerns being slipped in as a 'compromise' without causing a SOPA/PIPA-style blackout.
Thankfully, my employer, who I do not presume to speak for under any circumstances, has been active in campaigning against these stupid laws.
Some people say that "Oh, SOPA/PIPA isn't a good solution but another law might be OK." I, however, think that pretty much any law passed by a congress that is both as unwilling to understand and essentially corrupt as the one that America cranks out every 2 years is probably a bad idea.