I don't have one. Not sure why you feel we need to respond with 'humour'. What would you do if someone you didn't know walked up to you and mocked a family member? Would you crack a joke to show what a good egg you were?
They are fucking wankers and should be treated as such. Think about it.
I don't, but I think it would shut them up. If someone on the street were doing most of their communication by singing or chanting, I would assume that they were a bit odd. Same social rules doesn't apply on the stands. I'll try to elaborate why I think humour would be suitable for dealing with this in a somewhat confused rambling below. I apologise in advance, haha, and please try and keep an open mind, I'm only letting my thoughts roam.
quinny, you have some interesting points. I think that ticket prices are a factor, but maybe not the most important one. I think that the Kop might be a bit too "cosy". Older ST holders who used to sing their hearts out are not up to it to the same extent, but they still remain in the Kop because the ones that they used to sing with are also there still. In other countries, the "Kop" are a place where you go if you want to get a cheap ticket and sing. It will be rowdier and you can't expect to see much of the game if you want to remain seated. Usually, the older generation moves over to the main stand(s) where they can join in occasionally but still have a higher level of comfort with better seats etc. These tickets are more expensive, but they are in a better position to afford this now and they prioritise a good footy experience more than a loud atmosphere. In the Kop, you can usually sit throughout the entire game. There's no need to sing unless you want to, people won't give you looks for being quiet. Why then move to the pricier main stand?
I don't know wheather it's a cultural difference or only strict enforcements of the all seaters. I'm not English, nor Scouse. My local team is AIK Stockholm and the atmosphere is usually loud and aggressive. In the "Kop" section (norra stå), you have to expect that there will be flares, smoke grenades, bangers and if anyone tried to force people to sit down, there would likely be trouble. When people on that section becomes too old to be arsed and want to focus on the game, they move to the main stands instead. Tickets are reasonably priced, but not dirt cheap and it's only about £10-20 difference between the most expensive tickets on the main stand and the "Kop". The EL-matches usually fill only half the stadium, but it's almost even louder, because it's only the most devoted that will go even though the tickets are usually very cheap for these games. I went to the AIK - Napoli game and it was incredibly intense throughout, but you could almost touch the hostility in the air. A few AIK fans were stabbed in Naples, and in the second leg, Italians were chased around town all day.
I'm not saying that Liverpool have or should have hooligans chasing people around if they do or sing something stupid, but it's their way of "reclaiming the kop". They take it by force, and it can be grim. Liverpool is a friendly club with very well behaved supporters, and that would never happen. It's a working class club from a beautiful and friendly town with friendly people, but the reaction to this great club being bullied is what? Nothing. Ajax were and are taunted by their rivals for being jews. They have always been supportive of the Jewish community in Amsterdam and are non facist. Their response was to adopt the taunts and start chanting "Ajax joden, superjoden" etc. They made it their pride and it united them even more. AIK were being called rats, and it is now their fans' symbol and an informal nickname for the club. Scousers are being taunted for being thieves and unemployed/poor. It's fucked, yes, but one response could be to take pride in the working class background and emphasise that and turn it in to something beautiful. Shankly's socialism, Scouse solidarnosc (personal favourite) etc. I would suggest that this would be a suitable option for the club and it's culture. The thieving is trickier, it's hard to turn it into something positive, so why not use the Scouse wit that you are famous for to disarm it? AIK doesn't do wit, instead they use intimidation. Wit is more of the Liverpool way to go, and I can't see why not give it a try. As people already pointed out, fans that sing ignorant songs are c*nts, it's just a suggestion on what to do about it. Other suggestions are welcome.
*Edit: And I agree that if they could move the "singing section" of the Kop down to the front, it might be an improvement. I'm not too involved with the different fan groups (RTK, SOS etc.) and don't know what the relation to LFC is, but maybe one of these groups could discuss the possibilities with the club when they are redeveloping Anfield.