WBC make their living by picketing and then suing for rights violations. They spend up to a quarter million per year doing that stupid shit and the whole racket depends on publicity - if the oxygen of publicity was withdrawn they would wither on the vine.
That said, while the "Lame" video did make me laugh, I think this one is my favourite counter protest: http://www.youtube.com/watch?v=j7Of_2ykZpQ
I suspect that if they do show up at Comic Con the attendees will be...rowdy. Which is what WBC wants. What was done in the video I linked is a better solution.
And frankly I expect that the WBC will go down like Capone in the end - tax fraud. When the "church" is almost exclusively family members (with only 3-4 exceptions) then it is starting to cross the line in to whether or not it is a "church" at all and thus lose tax exempt status (I read recently about a swimming pool on their compound that was quickly filled in - wondered if the IRS got close that time).
Like many countries in Europe they are refused entry to the UK. Like many countries - including the USA - free speech is an illusion and is controlled by legal checks and measures. I believe that their kind of incitement to hatred is not permitted (we don't allow certain music acts that sing about burning gay people to death either).
Their habit of picketing the funerals of servicemen is, of course, reprehensible and I believe that there was a change in the federal law in the US that bans protests within a certain distance of a cemetary. WBC would, of course, love it if someone took a swing or tried to chase them off because then they could sue. I believe that the Patriot Guard do sterling service and that they welcome anyone who wants to ride along when these pickets happen so long as you don't let yourself get provoked.