A few days ago someone shot people while pretending to be a police officer. Someone impersonating ICE for kidnapping isn't out of the realm of possibility.
Or are you just restricting this logic to plainclothes officers, who aren't wearing uniforms at all?
Since we're all clutching our pearls, we might as well clutch all of them.
If the same acts are/were committed (i.e. ditch the sex trafficking example because the .gov doesn't really do that) what makes their misdeeds not equivalent to those of the non-state actor?