Since, y'know, aside from the supposedly intended audience, you and every other leftist ideologue on the planet seems to be able to "hear" them, too. You and your brethren would be well served by looking into the psychological concept of "projection" to best explain why y'all are so attuned to these whistles meant only for others. I fact, though, I suspect the only whistling to be heard is the sound of the air rushing into one of your ears and out the other through the empty space that lies between.
It could just be that the codes the moron conservative Bros use are worse than useless. Doesn't change the intent.
That said, I'm not certain why dog whistle is being treated as a liberal phrase. It really doesn't have a partisan bias.