This analogy fails because virtually everyone goes through life without becoming a murderer, where these people believe literally no one goes through life without being racist. A better analogy would be: is it reasonable to condemn people that refuse to stop being gay? If you really believe it's just something you are, that's part of your core and can't be eliminated...
"Wow, that guys wife is hot and I thought about having sex with her, oh no I guess that means I am an adulterer so I might as well actually have sex with her".
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".
I mean, if you're trying to point out that the people who believe that everyone is racist is a silly belief because it leads to absurdities, then I agree, welcome to the club. My point is not to justify that thinking, but to point out that they exist and so, to them, moral progress is apparently a fiction and so claims of "who wasn't racist in the past?" is not persuasive evidence that we're better now.
