I think this is just stirring the pot a little. Regarding Islamist Mexicans, is there a case of Islamist Terrorists coming over? We should really be screaming over Canada's lack INS control there. They let everybody there, foreigners no this and it's (was) easier to get here legally (or not).
"Abdel Hakim Tizegha, involved in the millennium plot, sneaked across the border posing as a Mexican migrant."
That Algerian cell was going through CANADA!!!
That said, I'm not a alien sympathizer, just focus on the urgent crisis on our northern border were terrorists come in.
An Arab can more easily disguise himself as a Mexican than he can a Canadian. Although your larger point is right on...ALL borders need to be secured.