I see your point here, but the situation of Reconstruction is a little more complicated. Lynchings did go up after the Civil War, but the reason that lynchings were less common before the Civil War is that White slave owners owners (and their supporters) viewed Blacks as

property. You don't kill your property--you whip, rape, brutalize, dehumanize your slaves, but you keep your them alive to work for you. Once White slave owners (and their supporters) no longer owned Black people, they had to use terrorism (lynchings, cross-burning, etc.) and Jim Crow laws to keep Black people subjugated.

Racism was more thoroughly systemic in the south (which is where the lynchings took place) but you didn't have to wear a white robe and hood to buttress up the doctrine. Most White people (like the bishops addressed in the Letter from Birmingham Jail, characterized by Dr. King as more harmful than the outright racists like Bull Connor) sought to maintain the status quo, which meant they supported White supremacy.

I don't think Whoopi Goldberg intended to support or deny white supremacy in her remarks. I think she wanted to reserve racism as a form of discrimination against people of color. I disagree with her thinking. White supremacists are as likely to be anti-Semitic as to be anti-Black or anti-Hispanic, just as they are anti-Islamic. Look at the Republican dog whistles using George Soros as emblematic of some kind of Zionist world domination.

To sum up, the form of racism we call white supremacism still exists as a powerful force in politics (and not just in America). In trying to speak out against the ignoring of racism against Blacks, Whoopi Goldberg (in my view) unintentionally promoted white supremacism. If you want an example of a Black plantation employee deliberately supporting White supremacism, check out Candace Owens' comments about Hitler and her defense of Trump's "nationalism."