Anecdotally, and interestingly, I've only ever seen the phrase "virtue signal" from the alt-right/white supremacist/Trump supporter group. I think I understand what it's trying to convey, but it seems to be used anytime someone sides with something with which that group disagrees. It's like a "dog whistle" for white supremacists and personally when I see it used, it makes me question everything else that person said.