I kinda figure if he is gonna do that he should at least be nice enough not to exclude 3 of the chapters.
Without seeing what it really said, I can't comment too well. But, I would try to take it as a joke. Especially if you're calling it a "roast". If that is what the author called it, then take it as a joke because that is most likely what everyone else will think.
If I heard something like this as a new member, it would most likely not affect my pledge-ship. By that time, they know what rush was about and what their sorority is about, so I don't think it will make people want to de-pledge or anything.
But, all of this is just personal opinion, so take it how you will.