Also I think people misunderstood. Makarov accepted Rose and Swift into the guild because they were who he was watching. Nobody else has yet shown a reason why they should be accepted. Rose and Swift learned something, and in seeing regret and guilt in Rose from the mention of having hurt one of her future guild mates, that showed Makarov that she was a good person and that's why he welcomed her to the guild. 

To everyone else he said 'welcome to Iron Tree' the same way someone would say "Welcome to Walmart"