I agree that most of the witlesses will not respond to the pickets, aside that the hounders are going to create trouble for those doing the picketing. You will probably make those who are studying think twice before joining the religion, however.
I don't see what is all that horrible about standing at the Kingdumb Hell with signs directing people to web sites that will expose the religion. You will probably get very few active witlesses to look it up, but the studies you prevent from becoming witlesses might. Additionally, it will make things harder for the witlesses in field circus when their calls quit, discouraging them and making a chance that they will realize what a waste of time it really is--even if they do not themselves visit the web sites. Just don't actively interfere with people entering and leaving the Kingdumb Hell or disrupt the boasting session inside.
What IS stupid is picketing by ranting "Get Saved". Most of the witlesses believe they are saved, and that their spiritual "food(??)" is being served at the Kingdumb Hell. Or, the "Hell phone" rants--acting like a clown is likely to make the witlesses not take you seriously. A quick reference to a web site that exposes the cancer for what it is is usually effective, because people are likely to remember the web site (sort of), pass by, get curious as to what the site is about, search for it using their favorite search engine, and get to that--or a related--web site.