What exactly is a “racist dogwhistle”?

In addition to what other people have said, it’s called a “dog whistle” because dogs can hear higher pitched sound than most humans, so a dog whistle, a whistle whose purpose it is to command a dog, is largely inaudible to humans while still able to be heard by dogs.

So it’s a “racist dog whistle” because it’s inaudible to most people while still being heard loud and clear by racists.

I hope that context makes it make a bit more sense why coded language that sound innocuous unless you’re in the know but is actually racist is called a “dog whistle”

a “dog whistle” in politics is a phrase that only a certain group will understand the message of but to most others it won’t mean much. Such phrases are a way to make controversial statements without most people realizing.

The archetypal example was the Nixon campaign’s focus on “law and order.” Given that the disorder he was implicitly referring to was the unrest of the civil rights movement, it’s quite clear that the message was, “I’ll fight the civil rights activists.” Saying that directly would have, of course, been deeply unpopular.

It’s a phrase or word or meme that will probably not mean anything to most people, but to those ‘in the know’ it’s clearly referencing a racist viewpoint.

An example is posting about (((Bernie Sanders))). To most peple it just looks like weird punctuation. If you’re in the know, it’s bringing attention to Bernie Sanders being Jewish.

The number 88 in white supremacist circles is a coded message. The 8th letter of the alphabet is ‘H’, making 88 ‘HH’, which is code for “Heil Hitler”.

If you don’t know this code, the number 88 has no special meaning to you. See it on a bumper sticker and it doesn’t stand out.

If you’re a white supremacist, and you see that bumper sticker, you know something about the owner of that truck. This message is only one that those ‘in the know’ know, allowing them to identify each-other without being identified by others. It’s called a dogwhistle cause you can only hear it if your ‘ears’ are tuned to the right frequency.

Language that seems innocuous but to a certain part of the audience will be understood as something more sinister.

For example, someone might refer to “the people who control the media”, and the general audience knows that there are people high up in media with influence, but this could also be a nod to far-right antisemitic conspiracies. Obviously that example would fall victim of being really hard to tell when someone is dogwhistling and when they’re simply taking a dig at someone like Rupert Murdoch, but that’s sort of the point.