Oxford Dictionary:
Prejudice, discrimination, or antagonism directed against someone of a different race
based on the belief that one's own race is superior.
‘a programme to combat racism’
- 1.1The belief that all members of each race possess characteristics, abilities, or qualities specific to that race, especially so as to distinguish it as inferior or superior to another race or races.
Note the highlighted part of the definition. It is a Belief. Unless someone specifically states this is their belief, when yo assign a motive to someone without that explicit statement, you are projecting your own beliefs.
No one can read minds.
Please do NOT conflate prejudice or stereotyping as racist, as they are neither. They can, however; be a basis of racism if the person confesses to being a racist.
You defined "Racism". I defined "Racist".
And you are right, no one can read minds. However, a person does not have to confess to be a racist to be a racist. The belief that his own race is superior makes him a racist whether he confesses to that belief or not, whether I know that person is a racist or not.
I am not of the habit of going around calling people racist; however, the speech and actions of some people leave little doubt. I, for example, do not believe Trump is a racist, but I do believe he is often racially insensitive. On the other hand, there are some people that openly state that their race is superior to another. If those people are being honest,then I can conclude they are racist.