Personally, I think perhaps their names should be passed about to other convention heads (after law enforcement, of course), but they shouldn't be publicly named and shamed. Just silently ban them from conventions. Naming and shaming is ineffective.
This isn't a matter of conventions, really, sexual predators shouldn't be tolerated anywhere. I believe that conventions do need to have a zero tolerance for the sexual predators and perverts who go 'too far'. People need to stop with the excuses 'She was asking for it, wearing that skimpy cosplay', 'It was just a joke to do with the anime', etc. I have stopped going to Supanova simply for the amount of men who disrespect female cosplayers and the personal experiences I've had with these sorts. Last year my behind was grabbed twice, and my friend and I had to hear sick perverted comments directed at us from a group of men tailing us. We left straight away. Especially in the big conventions where staff and security are low, I've heard this happens a lot. It's sad that we as young women and as cosplayers can't feel safe at some conventions. Event organisers really need to up their policies on perverts and photography, and seriously need security all around the venue instead of just at the door.
The "shaming" part of your question throws me off; that part seems a little... "inhumane". Someone convicted as a sexual predator probably should not be attending something like that. I have never attended a comic con, but from what I have read from others, some cosplayers have enough troubles trying to fend off grabby hands, so I think a sexual predator should probably be banned from public events period (though I don't know how it could be done). Especially if that person likes young children.... Those conventions can just be full of people!
I voted yes after thinking about it. I feel like if someone is a known sex offender (like BriguyZ said above, that term can mean rapist where I come from), then the public as the right to know about it, so they can be vigilant about such things. I can see how there'd be sex offenders at conventions like this, because some people can dress up as scantily-clad characters, and unless you're at a beach watching people wearing swimsuits, there's not many other places where people dress like that. For the people attending these conventions, I think they should be aware of that, and if there is a sex offender there that they know, they can avoid that person if they want. Though actually, I feel like if a known sex offender is in the area, then the people at the doors of the convention should know what they look like, so they don't let the person into the convention. I've never been to a convention before yet myself, so I'm just assuming they have people at the doors, since you usually pay to get into these, right? If someone committed a crime, I think others have the right to know about it so they can make their own decisions about whether or not they want to approach that other person, and so they can stay vigilant. If someone committed a murder and is walking around the area, I'd like to know. Same if someone was a known rapist. Not like my country really punishes criminals anymore, so there are people like this that are still walking around cities and whatnot. Y'know, because it seems like those crimes aren't a big deal in government eyes anymore.
Problem - where I come from, an 18 year old who has fully consensual sex with his 16 year old girlfriend can be a 'known sex offender' simply because the 16 year old girl's parents didn't like that she had sex and wanted to punish the boyfriend for it. He can then be forced to suffer through a PERMANENT criminal record and be required to register and report his status TO EVERYONE.
That's ridiculous. "Known Sex Offender" registries are broken, and until they're fixed, I am completely against naming and shaming. Ever.