It’s not about hating fat customers, it’s about them wanting freebies or allowing them to encroach on other passenger’s space. At the end of they day, passengers are renting space on a flight going from A to B. It isn’t any more out of line expecting someone who occupies two spaces to pay for them than it is for a normal sized person to expect to be able to use the space that they paid for without someone spilling over into half of it. Should parents traveling with lap children also be able to demand that the airlines give them free seats so that they can use a car seat?