They are mechanically playing a tabaxi but cosmetically playing a human. If I tell you about a fight in my campaign where the players fought ogres, but that I reskinned them as purple-people-eaters, would you honestly tell me that they defacto did not fight ogres?But see, if the position is existing vs not existing there really isn’t a mutual solution.
then they defacto aren’t playing a Tabaxi but playing a human with different stats.
It was one example plucked from infinite possible examples, illustrating how two people with opposing views might have an adult conversation and arrive at a mutually satisfactory conclusion.
Another possibility might be that the DM allows the tabaxi, but warns the player that they will be viewed as a monster by townspeople. Which allows the player the opportunity to be a master of disguise, or take disguise self, or play a druid with wild shape and pretend to be someone's pet, or stay out of town and accompany the party via familiar.
Without knowing the specifics involved and the precise motivations of both parties, I cannot do more than speculate regarding potential solutions.
The point was simply to maturely discuss the matter and try to find a solution both parties are satisfied with.