The liars fall into 3 camps.
1. People who are repeating what they've heard without actually doing any research of their own.
2. People who think that this immigration issue isn't getting enough attention (the lies and exagerations are their versions of shouting at people passing by on the street corner).
3. Professional disruptors (e.g. various 3rd parties left and right, Democrats, avowed leftists, Moby trolls, DK and DU misfits, etc.).
The 3rd group tends to claim that President Bush is somehow the "enemy" of the Right, as if he is out to get us, throw us into gulags, etc.
The other 2 groups just need to be reasoned with.