Sure, but the comedy isn't necessarily a reflection of their true views. Much like an actor, comedians are playing a part when on stage, a character. Also things that were once societally acceptable can become unacceptable over time. So comedians may have made a joke 10 years ago, majority of people found it funny and everyone moved on, then 10 years later someone digs up the clip and now it's inappropriate. Pretty impossible task for comedians to essentially 'read the room' ten years into the future.
The latter past I agree with you with. But:
"Sure, but the comedy isn't necessarily a reflection of their true views. Much like an actor, comedians are playing a part when on stage, a character."
Isn't that also on her to establish? If she's being critical of the behaviour and not just reveling in it, isn't that also her responsibility to make that clear just as it's her responsibility to make the joke funny? As Sarah Silverman herself says, there's a definite habit of white liberals to just imitate racism with nothing to differentiate it and then declare it to be fundamentally different because they, the person performing, aren't racist. She's done it herself in her comedy before and been called on it before.
I don't really care about the movie's hiring process here, they can do what they feel is appropriate. They have no obligation to hire anyone. And again, I also feel that Sarah Silverman has grown and think that's worthy of praise. But I just feel like these sort of threads reflect a lot of anger from people who are asked to think about the things they do and say and choose to instead lash out because they won't want to expend that effort.