Sincere concern that was pretty much non-existent when the bulk of these 12 million illegals were pouring into the country (during the 1990s), creating the untenable situation that Bush inherited.
This is nothing but a pile on. After six years of wall-to-wall Bush bashing in the mass media and popular culture, a lot of people were just looking for an excuse to join the party. This issue gave them one.
No, after 9/11, and the fact that most of the hijackers were here illegally, any sane person would have sealed the border and taken active measures to throw millions, not all, of the criminal aliens out of here.