Barry was wrong. He wasn’t a racist, but he was wrong on that issue, and he admitted it in later years. As did William F. Buckley. No matter how the bill was corrupted later on, how is the basic idea of equal rights for all Americans unconstitutional?
It wasn't,of use. But the provision that set in motion the references for minorities clearly were. And the Federal interference in employment, housing, and other such matters (impinging on property rights) cannot be justified in the Constitution. It's one thing to invalidate discriminatory laws. It's quite another to violate the Constitution to set up new and different discriminatory laws. That's what the 1964 Civil Rights Act did.