Mothers of boys not parents of boys? Do the men have no part in raising their son?
My mum's friend had a similar experience when she was a teen, some thirty odd years ago. After getting too drunk on a night out, she left her friends and got a taxi home. The taxi driver raped her. She ran to a nearby house for help where the male resident also raped her. By the time a third group of people found her, the woman was so traumatised, she wouldn't let them help her, convinced they wanted to assault her. They had to call the Police, fortunately, as it's thought, if she'd made it home, she would not have reported it.
They never found the taxi driver. The second man was arrested and I believed jailed for his part.
Although he never gave an explanation, it was thought at the time that if a convenient victim had not fallen into his lap, he would never have committed rape. He'd never been in trouble with the law previously and was happily married with children, holding down a decent job.
The Police believe because the victim was begging him to take her home and not the police station, he thought he'd get away with it. If he had taken her home, instead of throwing her out onto the street, half naked, for the third group of people to find, he might well have gotten away with it. As it is, he couldn't take her home because his kids were in bed and his wife was due home 
I do believe this is not a minority of men, it is a sizable portion, many of whom would never admit to being a rapist because they don't identify as one until a perfect opportunity comes along.
It's also a male problem and only males can stop it. The few decent men around need to start shouting very loudly against this. The media (and the men who control it) need to change the way women are viewed and men need to teach their sons that, no, it is not okay to speak about or think of women as sex toys.