In the neighborhood back then "ALOT" of people suspected he was "NO GOOD" however, at the same time were really confused because a "RAT" was "NOT" allowed to "KILL" and Scarpa was killing on regular.

So there was confusion.

On top of being Very Scared to blurt that out in fear of Scarpa finding out and killing you.

Lastly he had a "HUGE" crew on 13th ave, that brought in cash for the family.

I do not think anyone knew for sure
I believe they more so suspected it.

He was too strong, too feared to act with out proof.
His crew would have gone to war.

I think the Persico's knew to the extent of Massino knowing Brasco was a FBI agent,

Massino suspected it however, had no proof, so he kept his distance from Brasco and did not get in bed with him.

So I remember being young at the time and the older guys while trying to make a point to me, asking me and saying, dont you think it strange that, He has never gone to jail look at everyone else that is on the street and as exposed as much as he is, they all either went to jail (For a LONG TIME), or are home from jail, or have recently been arrested, Not Scarpa.

Occam's Razor dictated back then that we was a R.A.T.