Why yes, a history of overt racism in the republican party probably just suddenly disappeared! This stuff by no means lasts a full lifetime or propagates through generations!
The racists on the left think that we need to pump minorities full of welfare and government services in order to better subjugate them for their own benefit. The non-racists on the left think welfare and whatnot will help those people.
The racists on the right think that the minorities are a lost cause, dead weight to society and that we shouldn't waste a penny on them. The non-racists on the right think that we we got the government out of their business as much as possible these people would be able to help themselves.
Whichever group of non-racists someone's world view aligns with you will have a hard time spotting them on your own side because their racism just looks like good policy and you will see many more on the other side because their bad policy looks like racism.
The republicans probably do have more racists in their base because they're the whiter party and for historical "convince the poor white man he's better than the black man" reasons but IMO when it comes to actually pushing policy the racist party is whichever one has more policy you think is bad.
I have never once in my life encountered this hypothetical racist leftist, and a I've met a fair variety of racists. Why would you pick this topic as one to be a whataboutist about, when it's really not that ambiguous in the current US political climate.
If you thought that easy access to welfare was bad for people then you'd have met a hell of a lot of leftists who want "racist" policy.
My whole point is that one's evaluation of what is and isn't racist policy (assuming one believes in systemic racism in the first place) is based on what you consider good. Take a step back. Assume both parties believe that what they want is good for people and then assess the situation.
I'm not denying that there's racist hicks in the republican base. There's some racist hicks in the democratic base too (the stereotype of the waspy union worker who votes a straight blue ticket didn't come from nowhere) though IMO they're likely smaller in proportion of the party's base.
If you thought water was piss you'd have met a lot of people that like to drink piss.