You can meet some old people today who still have very wrong views about minorities and immigrants, let alone people who lived in the 1700's.
You're simultaneously underestimating the people who were here before us and our ability to adequately scrutinize their moral fiber. Of course, if by "people", "person" or "anyone", you mean the powerful, wealthy elite of the US, it's another thing entirely.
These kind of biases are impossible to remove just with laws.
If you turn off binary thinking and start thinking in degrees of effect, the fact you may naturally have some aversion to people that are not like you isn't a fucking excuse to genocide a group of people because of what they look like.
Almost all the excuses worded like the ones above that I've seen are from hard racists on why they shouldn't have to change there harmful behavior to others by wrapping in infantile sayings like "Jon was born gay and I was born to burn crosses".