The AFL-CIO members who booed John McCain seem to disagree with the union leadership. I found that to be pretty common when I was a member.
I don't think most of them agree with the union leadership at all. They're smart enough to know that their jobs will be scarce and their wages undercut if illegals get into the union.
The more illegals who get their foot in the door of American jobs, the worse off the American middle class will be. We will be dragged down to their wage level.
Who will pay the bills when the takers outnumber the givers? No one in Washington will answer that question, because they can't.