Given how venal and rough Malory is reputed to have been in real life, and definitely was as an editor (he chopped out all the romantic soliloquising of the de Troyes originals and replaced it with extended battle scenes, like some sort of medieval Paul Verhoeven or something), it's possible that we're supposed to find Galahad a dislikeable sanctimonious prig. Malory likes 'em flawed, bitter, violent and sexy.