The question is, why has it become popular for white supremacists to flash this hand sign? If they are intending to convey that they are white supremacists and

The question is, why has it become popular for white supremacists to flash this hand sign? If they are intending to convey that they are white supremacists and we are successfully understanding the message then that is what the hand gesture means. It's like a new word. The trollish origin doesn't change the fact that it has this new meaning in these contexts.