Here's my take on this, when I was in Europe earlier this year with my wife, I never had any problems with non-Europeans, in fact a Black worker from Sierra Leone who was working at the airport in Zurich helped my wife & I get into the airplane quicker due to our disabilities, in Ireland, a Black man working in the bathroom actually put soap in my hands to wash it.
Meanwhile, I was getting scammed by some Moldovan girls in Dublin, & a Spanish lady selling bus tickets in front of a cathedral in Seville was trying to manipulate us to buy bus tickets.
The only black guy that seemed to have a problem was my last night in Seville, I was smoking my last cigarette, & the dude gave me a dirty look, & he looked homeless with drug problems.
In Scotland or Barcelona, can't remember where, there was this white guy who was getting very angry for some reason I can't remember.
While, the only people that didn't wanted to be recorded was this Spaniard in the train in Barcelona, but he walked to another part of the train, and then the Northern Irish dude, who looks like those white dudes in America that have a 6 pick, tattoos, and a cap, and did some time in prison, and this Spanish lady in Seville who just covered her face.
But of all of those three encounters, and it didn't get physical like what happened to you in Rome, I don't their race is the problem, I think those black dudes are drug dealers, and don't want to be recorded because they are selling drugs, I don't think they might be mentally ill, but again I'm not a psychiatrist, I think they are just paranoid and aggressive drug dealers, Ive seen many White people here in America, especially Rednecks who behave a similar way.