I think that this is wrong too, but I don't support the sex offender laws to begin with because you don't have to be a rapist or child molester to be labeled as a sex offender. Check out
http://www.sexcriminals.com/megans-law/ and pick a state, you'll find out that in some states there are convictions that require registration as a sex offender that don't involve rape or molestation. Check out Florida and Louisiana as a couple of examples.