I don’t know why you’re blaming the WWII generation for Ted Kennedy’s immigration bill.
If you read the debates when it was being considered you’ll find that Kennedy and his staff, who wrote the bill, lied through their teeth when they described the bill. You can fault the Congress who failed to vet it and then voted for it, but it’s hardly something that was endorsed by the public at large. It was a very dishonest bill.
The Presidents JFK, Johnson, the Congress, the Senate, more than half the voters, were all of the older generations.