That's just nonsense (the racist part). However, every single person on earth is subject to conscious and unconscious bias and to think otherwise is disingenuous. Those biases are a product of the environment we grew up in, the country we were born in, religious exposure (or not), political, cultural, etc.
I 100% agree. You're missing the point. It already IS a white character and we can't go back and change that. Why would a black actor want to come in and just rehash some already told a (dozen times or more) "white" story? I feel the same way about all the needless reboots that lack originality. I simply limited the scope to race due to the topic of the thread. If you don't think replacing a currently white character with a black actor isn't lazy, then that is okay too. You are entitled to that opinion. If Michael B. Jordan was cast as the next Superman, I'd be there opening night (of course, hoping he took it in a new direction and made the character his own).
Furthermore, I bet if you polled the black community you'd get varying responses there too, some agreeing with my opinion and some not. Why? Black Americans aren't a homogenous group of collective thought.