Near the end of Gulliver's Travels (part IV, chapter V), the narrator offers a list of differences of opinion that have led to warfare among humans.
Difference in opinions has cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether the juice of a certain berry be blood or wine; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire; what is the best colour for a coat, whether black, white, red, or gray; and whether it should be long or short, narrow or wide, dirty or clean; with many more. Neither are any wars so furious and bloody, or of so long a continuance, as those occasioned by difference in opinion, especially if it be in things indifferent.
The absurdity of fighting wars over doctrinal differences is a recurring theme in the novel—the best-known example being the warfare between Lilliput and Blefuscu over which end of an egg to crack open. In the quote above, Swift is, at least in part, giving silly-sounding descriptions of actual religious controversies. However, although I do not recognize most of the disagreements he lists.
The first examples, "whether flesh be bread, or bread be flesh; whether the juice of a certain berry be blood or wine," are obviously about the Protestant-Catholic disagreement about transubstantiation. However, I cannot identify any of the other disputes with certainty (although the reference to "kiss[ing] a post" sounds like it might have something to do with Catholic veneration of crucifixes). The disputes over coat color and composition sound like they might rather be nationalist differences than sectarian ones; I thought the colors, in particular, might be references to army uniforms, but, if so, it seems quite curious that the famous blue of the French army is not mentioned alongside the English red.
Alternatively, it might simply be that none of the disputes, except the ones about the reality of transubstantiation, were based on actual sociopolitical disagreements than led to warfare. However, it seems like that would rather diminish the power of the satire. So are the remaining disagreements that Swift lists identifiable as mocking descriptions of real religious or political issues?