Quote 4
I replied "that England (the dear place of my nativity) was computed to produce three times the quantity of food more than its inhabitants are able to consume, as well as liquors extracted from grain, or pressed out of the fruit of certain trees, which made excellent drink, and the same proportion in every other convenience of life. But, in order to feed the luxury and intemperance of the males, and the vanity of the females, we sent away the greatest part of our necessary things to other countries, whence, in return, we brought the materials of diseases, folly, and vice, to spend among ourselves. (4.6.2)
Gulliver blames increasing desire for luxury on England's exposure to other nations. And Lilliput is in a high state of corruption in part because of its ongoing war with Blefuscu. All the best islands, Brobdingnag and Houyhnhnm Land, are totally isolated. So, it would seem that staying put in your country would be a good thing? But this book is called Gulliver's Travels, and Gulliver uses the opportunity of his travels to offer useful critiques. If you try to isolate your nation from the world too much, doesn't that lead to Houyhnhnm-style of smugness?
Quote 5
I told him "we fed on a thousand things which operated contrary to each other; that we ate when we were not hungry, and drank without the provocation of thirst; that we sat whole nights drinking strong liquors, without eating a bit, which disposed us to sloth, inflamed our bodies, and precipitated or prevented digestion; that prostitute female Yahoos acquired a certain malady, which bred rottenness in the bones of those who fell into their embraces; that this, and many other diseases, were propagated from father to son; so that great numbers came into the world with complicated maladies upon them; that it would be endless to give him a catalogue of all diseases incident to human bodies. (4.6.4)
The lucky Houyhnhnms don't get sick, but humans do. And Gulliver seems to feel that all illness is the sufferer's own fault, the result of living in a decadent society with too much food, drink, and sex. What's odd about this is that Gulliver is, himself, a surgeon. You wouldn't think he would speak out so strongly against medicine when he is a student of it. Among the Houyhnhnms, Gulliver really is forgetting everything about himself – and isn't hypocrisy itself a sin?
Quote 6
He made me observe, "that among the Houyhnhnms, the white, the sorrel, and the iron-gray, were not so exactly shaped as the bay, the dapple-gray, and the black; nor born with equal talents of mind, or a capacity to improve them; and therefore continued always in the condition of servants, without ever aspiring to match out of their own race, which in that country would be reckoned monstrous and unnatural." (4.6.15)
The Houyhnhnms split themselves up according to color and do not believe in intermixing. Gulliver doesn't talk much about races explicitly, but do you think this point about the Houyhnhnms indicate a racialist agenda to this portion of the satire? Where else might we find signs of what Gulliver thinks of race?