Many roosters have a good sense of defending their flocks. Some, are simply too human aggressive and cannot be trusted. Small children are particularly vulnerable as their small size and herky jerky motions tend to "trip" the inner instincts in a rooster to defend his harm from intruders. Horror stories abound of small children getting malled and severely lacerated about the head and face. Like a boar or bull, the rooster must be respected. Genuinely nasty roosters need to be made into soup.
I am finding that the sweetest. friendliest chicks are usually boys. Of those, the ones that get loved on the most seem to grow up the meanest. I read a really good post about hand feeding the Cockerels. The theory was that if you hand feed the boys, they consider you mom. They grow up Species confused with no natural fear of people. I am not sure if that is true. I do prefer to keep my Roosters on the less cuddled side. Those that like to stay out of my touching distance don't cause me problems.
Fred was right on the money. Some are lacking in the intelligence department and attack the ones who bring food and water. Though most would say chickens aren't the smartest animals on the planet, they do vary in levels of intelligence, just like dogs and people. And it's heritable, so I refuse to breed from a rooster who can't figure out that his human caretakers are not the enemy.
Keep the ones who are calm around humans after their hormones have kicked in and they are breeding the hens, which is really the only time you can figure out if they are truly human-aggressive.