Explain this quote from Gulliver's Travels: "I cannot but conclude the bulk of your natives, to be the most pernicious race upon the earth."

You have cited one of the most important quotes from Gulliver's Travels, one that proves Swift wrote a true satire.  Here the king of Brobdingnag, after hearing all about England from Gulliver, decides that the English are "the most pernicious race of little odious vermin."  If you put this quote within the context of the novel, you will most certainly find that it is Swift himself who believes viewing high society and politics through foreign eyes may reveal violence, barbarism, and foolishness.  Further, one can extend the meaning of Swift's underlying meaning from simply the English government to the entire human race.