Goyle is one of Draco's two hulking henchmen. He is a Slytherin fifth year, and he is basically Draco's muscle. Goyle's father is also a Death Eater whom Harry called out in his Quibbler interview, so Goyle has his own bone to pick with Harry. Goyle attempts to ambush Harry along with Draco and Crabbe on the Hogwarts Express, but they pick their fight in front of a train compartment filled with D.A. members.
By the end of this fight, Goyle has been cursed from so many directions that he looks like a giant slug packed into a Hogwarts robe (as do Draco and Crabbe). Ron comments, "Goyle's mum'll be really pleased, though [...]. He's loads better-looking now" (38.201). Now, obviously Goyle is a thoughtless bully, but this violence hits us kind of the wrong way. What justifies the D.A.'s decision to hoist Malfoy, Crabbe, and Goyle "into the luggage rack and [leave] them there to ooze"? Why is the D.A. allowed to do these things to Goyle, when similar behavior from Goyle would horrify the D.A.?