In Partial Defense of Sarah Grunfeld
Grunfeld's follow-up was widely taken as evidence of her continued failure to understand the use/mention distinction. And I agree. Let me say that again, so that everyone is clear that this post is only a partial defense of Grunfeld: the idea that Johnson did something anti-Semitic is absurd and Grunfeld's attempts to seek redress should be laughed out of court.
But I do balk at the idea that the use/mention distinction is a foolproof barrier against giving offense. There are at least two cases in which mere mention of an objectionable opinion can still be harmful: triggering and rumor-mongering. In either such case, it would not be inherently absurd to insist that "the words still came out of his mouth."
We'll start with triggering. Some ideas can be extremely painful to contemplate, even if the person bringing them up is not advocating them. Merely being asked to bring certain things to mind can be hurtful, especially to a person who has experienced a trauma connected to those ideas. This is the reason that feminist blogs put "trigger warnings" on links to posts and articles that discuss rape in any detail, even when those posts and articles are condemning rape and discussing strategies for ending rape. Someone who is a survivor of rape may find being confronted with information about rape to bring up too many painful memories of their own experiences. I find it dubious in the extreme that "all Jews should be sterilized" is triggering, as I've seen no examples of other Jews stepping forward to say that Johnson's statement was triggering (in fact, I was reminded to post about this when the above link was posted to Facebook by a Jewish friend). But triggering is still a thing that happens, and to negligently mention an idea you should know has good potential to be triggering is a form of bias against the people who would be triggered.
The second way that the use/mention distinction may not be a defense is in the case of rumor-mongering. Here, someone wants to put some idea out there, but doesn't want to take responsibility for agreeing with it. So you just mention it. Some people say that Barack Obama killed a thousand puppies with his bare hands. I'm not saying he did -- in fact, I think it's silly -- but I'm just telling you that other people are saying it. This kind of transparent laundering of objectionable ideas through mentioning them instead of using them is condemned by the Associated Press Stylebook, and for good reason. It puts the ideas out there as something to be considered just as much as actually stating them as your own opinion would. Johnson's statement was highly unlikely to put the idea of sterilizing Jews into the public consciousness and make it a topic of debate (and post hoc we can clearly see that it did not in fact inspire such effects), so this line of defense wouldn't be available to Grunfeld. But it is a type of case in which saying "the words came out of his mouth" could be a legitimate response.