re: What changed political views and the animosity of parties so much in 2000?

You are somewhat on the mark here,
at least with the timing.

I went to a dinner hosted by the Alabama Policy Institute where the late Senator Tom Coburn spoke. Coburn was a Republican from Oklahoma. His message regarding President Obama pretty much stunned the crowd. He was highly critical of the birther movement and of those who tried to label Obama as a Muslim, un American or otherwise an illegitimate president.

The following quote on his Wikipedia page might not be word for word, but it pretty much sums up the sentiment-

quote:

---

”I love the man. I think he's a neat man. I don't want him to be president, but I still love him. He is our President. He's my President. And I disagree with him adamantly on 95% of the issues, but that doesn't mean I can't have a great relationship. And that's a model people ought to follow."

---

LINK


2008 was the election where the game truly changed, for both sides. From that point on the concepts of loyal opposition and respectful disagreement on issues went into steep decline.