In a perfect world any actor could play any role and people would accept it as acting.
But, as evidenced by the existence of JonFreeman, this is far from a perfect world.
White actors have used black/brown/red/yellowface for decades to mock and demean other races, while actors of other races have been excluded while white actors profited.
Similarly, straight actors have perpetuated stereotypes of gay people while gay actors have had to conceal themselves or be unemployed.
Redressing old wrongs is not the same as creating new ones.