Does she think about the sin of the wicked son in the Passover story, and how that sin might echo in her own life? This is not meant to be snide, but John and I lead a seder every year and I've taken to making my own Haggadah because I'm not comfortable with many of the traditional stories and blessings. The wicked child bit is something I've deleted. But anyway, to you, aren't I the one who doesn't know how to ask?
Bendekit doesn't explain why she finds the Wicked son (she calls him a child) so troubling. However I can only guess that she objects to labeling a "child" as evil. However I find this approach rather symbolic. The part of the haggadah dealing with the four sons is an educational part. It is in essence advice from the sages how to deal with four different personalities. As such all the characters are stereotypes, meant only as generalizations. What is important is that the sages include the category of "evil", or at least the category of someone with a worldview that can not be accepted. By deleting the wicked son, she is in essence deleting the opinion that anyone may have a view that can not be accepted. In other words she is denying that at some level there is an absolute truth - and more importantly an absolute lie. It is not surprising that Benedikt comes off in her article and response to Goldberg as someone who is incapable of having her own opinions She lives in a relativistic world where moral clarity is a very very tough act.
See this Volkh Conspiracy post which has a similar argument.