So what you are saying is that racism is defined by race,
NO! I AM NOT SAYING THAT. YOU AND ELFI ARE SAYING THAT.
HOW CAN YOU POSSIBLY MISUNDERSTAND AND MISREPRESENT SUCH A BASIC IDEA?
Racism and any bigotry is based on belief, a belief that the perpetrator is superior to the victim. It is not based on actuality or reality.
Racism and other prejudices are based on a taught response. To ascribe negative meanings to differences is not natural, it is something we learn, and is therefore something we can unlearn.
Now to take a simple case, not of racism, but of homophobia:
If a hetreosexual person is suspected of being gay, and suffers from homophobia as a result, it is pedantic and nonsensical stupidity to argue that the victim could not have suffered from homophobia because they were not gay. They were perceived as being gay by the perpetrator!
Similarly, if a person suffers bigotry because the perpetrator believes that they are superior due to taught prejudices, it is pedantic and nonsensical stupidity to argue that it was not racism, because the victim is the same race as the perpetrator. The perpetrators do not have the intelligence to inquire about the actual race or ethnicity of their victim. The perpetrator exhibits bigotry based on a belief and perceived differences.
"Racism and anti-racism is first a battle of ideas." Dimensions of Racism. OHCHR
To argue that bigotry cannot be racism because the perpetrator and the victim are the same race is completely lost on the perpetrator, but more importantly it detracts, diverts, deflects and dilutes from the "battle" against bigotry which we term racism.
According to your and Eldi's narrow and pedantic definition racism cannot exist:
"some scientists describe all humans as belong to the same race — the human race.
Ethnicity is the term for the culture of people in a given geographic region, including their language, heritage, religion and customs."
https://www.livescience.com/33903-difference-race-ethnicity.html
"
Racism takes many forms and can happen in many places. It includes prejudice, discrimination or hatred directed at someone because of their colour, ethnicity or national origin."
https://itstopswithme.humanrights.gov.au/about-racism
Finally, some thoughts:
"So we should start by understanding racism as a worldwide phenomenon that requires a worldwide response.
All societies, and all of us in those societies, must address racism in the forms that it manifests itself in our lives and cultures. ... But, as they emphasize, they are dealing with a common concern – the denial of equality to fellow human beings because of their race or ethnicity or nationality.
... Every one of us, whether we are conscious of it or not, are living out our lives in societies shaped by history. In all societies structures of inequality, including economic inequalities, have been laid down in the past. In a number of cases these structures have been based on or influenced by racist assumptions that, transmitted over time have continuing effects today. The challenge for all of us is not to be passive in accepting the hand history has played, but to work for positive change that can leave behind what has been negative about the past. A universal human rights era in which we now live gives us the necessary values and means to work to end such inequalities and the prejudices and attitudes that sustain them.
No one can be denied their human rights because they are different from others, whether by sex, race or ethnicity, work or descent, caste, culture, religion, skin colour or other grounds. The struggle to ensure equality of treatment for everyone is thus at the centre of all efforts to promote the universal protection of human rights." OHCHR