Suppose, in a conversation with a friend, she makes a policy proposal. You object, saying that the proposal would hurt the poor. Presumably she disagrees, but she wants to know more. She asks you for details as to why you believe her policy is harmful in this way. After hearing your reasons in more detail, she responds: she provides her own arguments against your claims, or perhaps she adjusts or modifies her original position to accommodate your concerns, or maybe she ends up abandoning the position altogether. Such is the normal (if a bit idealized) process of political argumentation.
Now suppose you make a different objection. You say her policy is antisemitic. Or racist, or sexist, or Islamophobic. Now her reaction is probably much different. She does not ask for more detail. She does not consider your reasons and then respond by contemplating whether to alter her original view, or even reply with X, Y, and Z arguments as to why your claim of antisemitism is wrong. In all likelihood, if someone is accused of antisemitism, their first and only retort will be to dismiss the argument out of hand. "There you go—crying antisemitism again!"
"-ism" claims, including but not limited to antisemitism, seem acutely vulnerable to this sort of preemptive dismissal. We don't treat them as arguments, which may be right or wrong but which ought to be considered seriously on their merits. We treat them as slurs, or epithets. They are often said to "shut down", "chill", or "censor" a conversation—as when Stephen Walt & John Mearsheimer referred to antisemitism as "the great silencer" in debates over Israel and Palestine. There's no partisan monopoly on this reaction—leftists often seem to consider it grievously unfair that when talking about Israel it is demanded that they seriously reckon with antisemitism, but they are paralleled in full by conservatives who throw a temper-tantrum when people like Steve Bannon or Sebastian Gorka are linked to the vice. If there's one thing everyone can agree on when it comes to antisemitism, it's that it's absolutely outrageous to implicate me or mine in it.
And this is ironic. There is nothing conceptually different between calling a policy "bad for the poor" and calling a policy "antisemitic". Both are arguments, which may prove to be correct or not, but whose validity ought to depend on substantive consideration. When people refuse to even engage in the argument over antisemitism, they're the ones shutting down conversation. They are refusing to engage in further discussion if that means grappling with antisemitism as a live question that deserves consideration on an equal plane. "If you're going to make me talk about antisemitism," they say, "then I'm going to take my ball and go home." In a world supposedly overrun with political correctness and hypersensitive millennials, there are no greater snowflakes than the man said to be misogynistic, the White person accused of racism, or the non-Jews told they are antisemitic.
What persons who claim to be "chilled" by antisemitism allegations are actually saying is that they have an entitlement to talk about issues that impact Jews without having to consider the issue of antisemitism while they're at it. But this is an absurd position to take; it's virtually impossible to imagine what could undergird such an entitlement. Not all "criticisms of Israel" are antisemitic (nor, it's worth noting, is there anyone who thinks otherwise—this is the ultimate strawman), but to speak of Israel without even considering the question of antisemitism is an exercise in gibberish—nor more coherent than trying to have conversation about affirmative action while taking the matter of racism off the table (which, unsurprisingly, people try to do as well). Antisemitism is not the only important facet of Israel as a political issue. But if you're purporting to talk about Israel in a remotely comprehensive way and you refuse to talk about antisemitism, then you're going to talk about Israel poorly.
At this point, those persons who often have indulged themselves in dismissing antisemitism, or racism, or whatever the "-ism" claim at issue might be, will attempt to retreat to a more defensible position. The problem, they'll say, isn't that these claims of oppression are never germane. The problem is that such claims are frequently abused. They're deployed too often, in cases where they're just plain wrong, where their only function is to smear or sabotage.
There is a kernel of truth to this—but it is a very small kernel, and people don't tend recognize just how much ground they are ceding when they make this argument. The nugget of truth is that if an "-ism" claim really is no different in kind than other potential arguments, then merely invoking it can't suffice to end the conversation. It rather invites an extension of the argument, one in which we fully and fairly consider the validity of the charge and how it ought to be addressed.
So to the extent that some actors behave as if the raw assertion "that's antisemitic" should be enough to settle matters, that is unjustified. If those on the receiving side are wrong in just walking away, then neither can those making the accusation simply drop the mic and move on. The requirements of consideration and open-mindedness cut both ways. That point has particular resonance in the rare cases where the cry "I'm being chilled" comes attached to actual instances of censorship—a conference being canceled, a lecture being shouted down, or an academic being fired. Such a response is wrong even if the speech really was hateful in nature (I am part of the tiny group who thinks both that Steven Salaita wrote antisemitic tweets and that the University of Illinois was wrong to rescind his academic appointment).
But more frequently, there is no such censorship and there is no such "mic drop". It is nothing more than the "-ism" allegation itself—unadorned, existing as naught but speech—which is said to have this chilling effect. In those cases, the ground ceded when persons retreat to saying that "-ism" claims are "abused" is massive. For stripped of all its presumptive gloss, the new argument boils down to "people call things antisemitic when I don't think they are." And that—believe it or not—shouldn't suffice to establish that the argument isn't worth considering. "All criticism of Israel is antisemitic" is absurd on its face, it can be dismissed out of hand. "My criticism of Israel is antisemitic" is not, and cannot. But this is what people functionally are saying: discourse about antisemitism is corrupt precisely as far as it suggests that I'm potentially implicated in it.
Unless we are supremely confident in society's default instincts regarding what is and isn't antisemitic, there's no reason to privilege people's gut sense of unfairness—how dare you call something antisemitic when I don't think it is!—over the need to engage in open and fair argumentation. That doesn't mean we'll ultimately agree with the antisemitism claim. But it does mean we can't treat it as an affront (or worse, an act of censorship) when we're asked to give it a fair hearing.
Contrary to popular belief, members of marginalized groups do not typically make discrimination claims just for the joy of it, nor do they do it as a bad faith ploy to silence their political adversaries. When it comes to antisemitism or anything else, the charges are almost always made for no more complicated a reason than that the claimant believes them. If we think they're right, we should adjust. If we think they're wrong, we should explain why. In all cases, we should strive to be thoughtful, charitable, considerate, and open-minded. The one thing we shouldn't do is simply refuse to have the discussion. The ultimate form of chilling speech is when we simply refuse to talk at all.