"Sex offenses are about power and control over someone more vulnerable. You don't need a penis to be a sex offender," Sara Totonchi of the Atlanta-based Southern Center for Human Rights told AFP.
"Many sexual offenses involve indecent touching. So are we going to chop off their hands?"
The conviction of Genarlow Wilson, a black American teenager, jailed in 2005 after being found guilty of child molestation for consensual oral sex with a 15-year-old girl is one example of the excesses in the US law.
At the time of Wilson's conviction, Georgia state law said the consent of both parties was a mitigating factor in sentencing -- but only if they were engaged in conventional, not oral, sex.
Wilson was sentenced to 10 years in jail and had his name included on the sex offenders register.
"Once you're on the registry, it's for life in Georgia," said Totonchi.
US state and federal laws have long required those convicted of a sex offense -- which can include everything from indecent exposure to sexual assault -- to add their names to a sex offenders' registery.
The US Department of Justice has launched a public, Internet-based registry, which lists sex offenders in all 50 states.
Those on the registry are subject to severe restrictions on where they live or work, and have to inform the police when they move.
"There is a provision that says those listed on the Georgia sex offenders' registry cannot live or loiter within 1,000 feet (300 metres) of where children congregate," Totonchi said.
"That includes, in particular, churches and school bus stops. School bus stops are constantly being changed, and they are everywhere, and sex offenders probably need to be able to go to church more than most people.
"So this provision is removing the potential for stability from the sex offenders' lives whereas the smartest thing to do if we want our children to be safe would be to encourage the creation of stability in their lives," Totonchi said.
Many states have so-called Megan's Laws, requiring them to provide the public with information on the whereabouts of sex offenders.
Megan's Law is named after seven-year-old Megan Kanka, a New Jersey girl who was raped and killed by a convicted sex offender who lived across the street from her, unbeknown to her family.
Opponents of Megan's Law say people who committed misdemeanours, such as streaking or urinating in public, could be convicted of sex crimes and listed on the offenders' registry alongside sexual predators.
"California's Megan's Law lists indecent exposure right there along with rape and child pornography as among the offenses that can get one included on the state's sexual offender database," Patrick Coleman Howe, managing editor of the state's New Times weekly, wrote earlier this year.
The state of Florida also toughened up its sex offense laws in 2005 following the sexual assault and murder of nine-year-old Jessica Lunsford.
The law, dubbed Jessica's Law, provides for a minimum sentence of 25 years in prison and lifetime electronic monitoring of adults convicted of lewd or lascivious acts against a victim less than 12 years old.
Jessica's Law has now been adopted by many US states.
But Totonchi warned that introducing chemical castration could see a fall in the number of reports of sexual offenses against children. "Eighty to 90 percent of sexual offenses against children are committed by someone the child knows, not by the predator waiting by the bus stop," she said.
"If the child thinks that this person they know is going to go to jail and be chemically castrated, they are less likely to report an offense."