RIR's have had that reputation for decades. During WWII, my grandmother had a big RIR rooster that she traded to a neighbor for two hens because he kept attacking my aunt, who was about 4 years old. OTOH, they also have a reputation for defending their hens to the death, so there is a trade off, I guess.I've heard a lot of people say they had RIR roo's become very aggressive, more so than other breeds
A few weeks ago I butchered 4 cockerels that my constantly broody BO hatched this spring, two RIR's and two red sexlinks. One of the RIR's was mean to the bone, while the other was sweet and friendly. A dog breeder I used to know would say that there is more difference in personality between individual dogs within a breed than there is between the personalities of different breeds, and I think it is the same for chickens, too. There are some that are good and some that need to be taken out of the gene pool in every breed.