I interpret the quote "silence is violence" to mean by not speaking out against violence, you implicitly support or contribute to it. People may disagree if this is true, but it certainly doesn't feel Orwellian.

First they came for the socialists, and I did not speak out— Because I was not a socialist.

Then they came for the trade unionists, and I did not speak out— Because I was not a trade unionist.

Then they came for the Jews, and I did not speak out— Because I was not a Jew.

Then they came for me—and there was no one left to speak for me.

Have you Googled the term? Apart from the first page or so being dominated by that very recent event of the crowd intimidating people and many other people conflating that event with that slogan, you'll find plenty of articles about what it means: that choosing to not speak out about an issue helps support the status quo. In fact, I've generally seen it used to try to persuade people who don't want to support the status quo that staying quiet or trying to "not be political" is in fact supporting the status quo.