I don't think it actually happens as much as these people like to say it does. It's just a convenient way to externally blame and berate those they don't like for things they were going to do anyway.

But to the extent that it does happen, it seems explicable with reference to the behaviour of children when told not to do something. Some evidently never grew out of it.

I'm not sure how effective it is, but I have heard of the concept of "rage spending". buying a product with the intent to enrage social or political opponents.

The idea makes sense, but these days people make it so blatant. So the merchant can make it feel more like a grift than simply trying to appeal to an audience.