Reverse racism is definitely a thing. To say it is not is similar to saying that the word 'murder' is only to be used for when a white person kills a black person. You can't change the underlying ethical status of an action by redefining it.
Reverse racism is a contradiction in terms because extreme prejudice is necessarily accompanied by the power of society's approval and legislation. While women and poor people of color may become intolerant, personally abusive, even hateful, they do not have enough power to be racist or sexist.
Reverse racism is a fully incoherent notion -- racism is a system of power and in the absence of power one simply cannot be considered a racist.
Reverse racism is a super-fantasy wherein the people of Middle Earth believe they are being systematically oppressed by Hobbits
Reverse racism is incoherent and nonsensical insofar as charges of so-called reverse racism are firstly an acknowledgement that racism exist, secondly that racism does harm, and thirdly, insofar as charges of 'reverse racism' are typically leveled in response to some project, policy, practice by a suppressed people to make the system more equitable, these charges reflect not the experiencing of being on the receiving end of racism, but rather reflect a desire by a privileged group to maintain a privileged status