I can only venture a guess, that they are not allowed for the same reason that Sam Francis is not allowed here, because of his occasional foray into somewhat bigoted commentary. The anti-immigration posters on FR, when they engage in reasoned debate, have shifted my personal opinion on the matter. But unfortunately there are a few folks involved in anti-immigration matters who also engage in anti-Mexican bigotry, such as the claims that they are inferior, that they could never assimilate (the same claims made against Southern Europeans a century ago, or Germans, for that matter, two centuries ago). That is where I draw the line. The problem is not inherent in the Mexicans who come here - it is from the sheer numbers, the illegal manner in which they come here, the movement of this country away from assimilation, and the welfare state that is a problem not just with immigrants but also with existing citizens.