And you, good sir, have not read the entire thread. There are differences in bringing in assets (mammets), names (crystal tower, Raubhan), it's not the same as lifting an entire character and her back story and inserting it into the next numbered FF title. Things like Costa del Sol and Rauhban are similar in name only: it's not like The Immortal Flames leader is walking around as a blue mage trying to kill you. He has nothing to do with XI's character: they merely share the same name.
Lightning, on the other hand, is the same Lightning from XIII. She's not an Eorzean-original, like most fanservice things we've seen so far. This is what's causing the distress.
I do agree though, it's just a marketing ploy to promote Lightning Returns, and similarly the miqo'te outfit in LR is a marketing strategy to promote XIV.