I'm black and white on the behavior. I absolutely agree with your point about biases being often not obvious.
In this case, though, the biases are so apparent that these employees can't be expected to interact with other potential employees. If an employee's behavior is so abhorrent you have to work around them, they should be replaced.
Another way to think of it - I'm sure the company has language in it's employee handbook around non-discrimination. These employees are overtly violating this language. By letting them stay on and accommodating their behavior, a clear message is sent that they're not serious about non-discrimination.
In this case, though, the biases are so apparent that these employees can't be expected to interact with other potential employees. If an employee's behavior is so abhorrent you have to work around them, they should be replaced.
Another way to think of it - I'm sure the company has language in it's employee handbook around non-discrimination. These employees are overtly violating this language. By letting them stay on and accommodating their behavior, a clear message is sent that they're not serious about non-discrimination.