Yes, and I'd argue this is the strongest form of selection bias in such circumstances -- and the one that takes the most courage to avoid falling to.

    First they came for ... and I didn't say anything.
    Then they came for ... and I didn't say anything.
    ...
    Then they came for me, and there was no one left to speak for me.

When people select themselves out of speaking up for others because of fear, the purity/outrage spiral can get out of control.