He is treated as an outsider by the boys; they were a closed circuit of sympathy with Piggy on the outside
Piggy was an outsider, not only by accent, which did not matter, but by fat, and ass-mar, and specs, and a certain disinclination for manual labour - repetition of and emphasises the length of that list and therefore the ways he is different - though interestingly these are all physical characteristics, and therefore shows how the boys are judging him solely on appearances