Handbasket: You take this out of context a little. The man who flashed his willy fifteen years ago could well have commited other crimes in the meantime, ones that are more serious and ones for which he has never been caught. Ergo, crimes which are not on his criminal record. Of course this is not the case for everyone convicted of a sex attack but there will always be a handful whose actions go unreported.
You are right that the issue of child sex often elicits a hysterical response that is ill-conceived and injust - but I think that has more to do with the fact normally rational people can be provoked to such extremes by the thought of this abhorrent act, especially in the case of the OP.
Also bear in mind that this is an internet forum and people don't normally act as such outside the net. How many cases of vigilantes attacking pedophiles do you hear about? Not very many. Imo, there are more cases of terrible pedophilia reported than vigilante efforts, so pedophilia is certainly a larger problem, though the media doesn't help by blowing it up to sensationalise.
However, the law views the convicted pedophile as always a danger. A drink-driver can be stopped quite easily - take away their car and license and monitor them so that they do not try to get back behind the wheel illegally. (Also, in my country it is legal to hand around the information of convicted drink-drivers, while is not for a sex offender... why, I don't know).
A pedophile is far harder to monitor. They can disguise and supress their desires for years, even decades. It is near impossible to root such perverts out and so everyone convicted of a sexual offence - no matter how minor or how long ago - must be tarred with the same brush in order to try and maintain some sort of balance.
I'm glad to hear you got over your bad experience but many do not. A guy I went to school with hung himself last New Years because of mental problems stemming from when an older relative 'diddled' with him as a child. As far as I know, he was never raped but it was sufficent enough to disturb him. Until child abuse becomes a mimimum in Western society, we will always have this conundrum.
But I digress. Fundies may want all homosexuals stoned to death, but by and large most homosexuals have not committed a crime worthy of death. However, fundies know that if they try to murder gays, they will get a loooooooong spell in prison, and most couldn't commit murder anyway, despite their beliefs. So they don't do it. People who write things like "ZOMG!!1 i will set u on fire u hideous shitstain!!!!11" (I know, I've told more than one fstdt quote author to DIAF) would not do this in RL.
Analyzing aside, if I were a mother I would want to know if there were drink drivers, drug pushers, ex-cons AND sex offenders of any type in my area so that I am well informed. Forewarned is forearmed, though it doesn't mean you can be completely paranoid.
PS - I do believe this quote is a troll as I can't find any evidence linking it to the Ayatollah (though he has said some pretty disturbing shit) and it comes from YouTube, troll capital of the internet.
Whew. Think I'm gonna go lie down now.