Too many people feed the trolls, and that's not how you should deal with them. These obnoxious individuals love nothing more than arguing over ridiculous matters, and in this case it was dealing with Merle being a racist d-bag. He was creating a problem for the whole group, and it was just too much to cope with in addition to the horde of zombies. They realized the best way to handle him was to ban him from the group, so they handcuffed his ignorant ass to the rooftop.