Well, they call him that, because the FBI was using people like at the time. And some of them probably were on the other side. It wouldn’t be the first time such an operation blew up in their faces. If the FBI is going to use a civilian asset, they better be damn sure they’ve vetted and prepared things properly. The planners of these riots may be bad guys, but it doesn’t help if the FBI is, even unintentionally, assisting them.
I think it was hard to tell who was friend or foe. It probably still is.