If someone said "Americans do X", there would be some pushback about "not all Americans". But somehow it's normal (expected even) to bunch all immigrants together into the "they were all desperate and decided to jump the fence" pile.
It's actually surprising that this point is so hard to understand.
Those who stood in line as you say also want to take people out of today's queue. Legality doesn't have much to do with it. In Britain it's called pulling up the drawbridge.
