Fear of incrimination by inaction

During the Chinese cultural revolution, students assaulted their teachers. During the French liberation, Nazi collaborators were shaved in the streets. The perpetrators are often described as being in terror of holding back, afraid of being seen as sympathisers, panicky scapegoaters, desperately inciting the mob against others to reduce the threat to themselves.

Is there a phrase or idiom to describe that fear of incrimination by inaction, specifically in the context of (metaphorical) witch hunts?

The men, afraid of [_____], shouted at the prisoners where the soldiers could see.

As noted by @BenjaminHarman: bonus points for conveying both the fear of being associated with a group and the fear of reprisal from another group.

"..., afraid of being tarred with the same brush, shouted at..."

Idiom: Tar somebody with the same brush

To believe wrongly that someone or something has the same bad qualities as someone or something that is similar (usually passive)

"I admit that some football supporters do cause trouble but it's not fair that we're all being tarred with the same brush."

www.thefreedictionary.com

I like Marv's tarred with the same brush, and here are a couple others:

• Guilt by association - An expression that is less idiomatic but means the same thing: "The men, afraid of guilt by association, shouted..."
• If you lie down with dogs, you get up with fleas - Conveying a very similar fear, this idiom would take a slightly different tack, albeit probably a truthful one for some, by saying: "The men, afraid of lying down with dogs, shouted..."