Deleting all of Cosby's TV shows and movies would still be wrong as they are a part of our cultural history.
No one is doing that though, there is a difference between no longer promoting something and erasing it from history.
Actually, there isn't in the case of copyrighted works. If the rights holder stops selling and promoting something without re-licensing it for public use, then it is dead and nobody else can legally acquire a copy. This is one of the reasons there should be a requirement in copyright law that the work must be made available or the holder loses their exclusive rights to it.
To stretch the Cosby link further, you might (quite reasonably) think things Cosby did in the past are funny and even have value beyond pure humour, as social commentary etc. If that were the case and you know someone who had been abused by Cosby, would you choose to put a Cosby video on for them and expect them to find it an enjoyable experience?
That is the situation MIT is in. They aren't just dealing with 'theoretical' students who might somehow be deprived of some value that only those videos can impart. They are dealing with real students actually effected by the situation at hand.
If you wouldn't knowingly ask someone you care about to be entertained by someone who had abused them, why would you expect MIT to ask someone to be educated by someone who harassed them?
I wouldn't ask them to watch something from their abuser, but that isn't what's happening here. No one is being forced to watch anything. They're not even being asked to. Worst case is if one of Cosby's victims happened across a rerun of his, they quickly change the channel. The MIT lectures are even less likely to be seen accidentally and the professor's name is clearly listed on it. Are you suggesting that the right thing to do is to eliminate every reference to a person just so that a few people who were hurt won't occasionally stumble across a reminder that their abuser exists? If so, where do you draw the line there? The MIT professor only violated sexual harassment rules and as far as I have seen isn't even charged with a crime. Is that really enough to warrant erasure of his work? What about a high school bully? Are they so tainted that they should never be allowed to participate in our culture again?