There is no truth to that claim at all. And liberals don't say that.
We already went through this..
Here are a few articles on the subject:
https://www.theodysseyonline.com/minorities-cant-be-racist
Racism comes from prejudice and the group with the prejudiced having power. All throughout history and to this day, white people are the majority group in America. Systematically, white people have the power and when you add prejudice you end up with racism.
When you have people of color in America, they are the minority groups. They don’t have the power like the white majority do. Hatred toward people of other races in cases of minority groups to other minority groups or minority to majority in cases of race, isn’t racism. It’s prejudice
https://www.elitedaily.com/life/culture/dear-white-people-why-black-people-cant-be-racist/1960206
Racism is the oppression of a marginalized group in a society that is based on white supremacy. If you are a white person, then you naturally benefit from white privilege.
This means that the exclusionary things black people are often accused of being racist for doing — creating a "Black Lives Matter" movement, attending historically black colleges, having a "Black Girls Rock" event — could never be racist.
https://www.thecrimson.com/column/between-the-lines/article/2018/8/10/gao-who-can-be-racist/
Another camp thinks primarily of institutional racism and factors in a person’s power to use their racist beliefs against others. As one African-American lead character from the 2014 movie “Dear White People” argues, “Black people can’t be racist. Prejudiced, yes, but not racist. Racism describes a system of disadvantage based on race. Black people can’t be racists since we don’t stand to benefit from such a system.”
https://atlantablackstar.com/2016/10/06/google-pisses-some-people-off-by-claiming-blacks-ethnic-minorities-cant-be-racist-toward-whites/
So can African-Americans really be racist toward the very racial group that oppressed them for so many years? The answer is a resounding “no,” according to tech giant Google and a host of other experts poised in debunking the myth known as “reverse racism.”
https://medium.com/humanist-voices/can-minorities-be-racist-a9ff8c7bc102: "On one end of the spectrum, PC leftists say there’s no such thing as reverse racism because minorities can’t be racist."
https://www.pambazuka.org/governance/black-people-can’t-be-racist
Black people can never be racist – we never had the tools or power to institutionalise racial oppression.
https://www.huffpost.com/entry/reverse-racism-isnt-a-thing_n_55d60a91e4b07addcb45da97
Some people simplify racism as one group not liking another, and think “racist” and “prejudiced” are interchangeable. But racism is a concept that operates on both an individual and institutional level.
At its core, racism is a system in which a dominant race benefits off the oppression of others — whether they want to or not. We don’t live in a society where every racial group has equal power, status, and opportunity. Yes, white people all over the world and throughout history have experienced atrocities like slavery and persecution. But in the very specific context of American history, white people have not been enslaved, colonized, or forced to segregate on the scale that black people have. They do not face housing or job discrimination, police brutality, poverty, or incarceration at the level that black people do. This is not to say that they do not experience things like poverty and police brutality at all. But again, not on the same scale — not even close. That is the reality of racism.