In Gulliver's Travels, what in the king of Brobdingnag's criticism makes you think that Swift was satirizing his own society?

Gulliver thinks that the king of Brobdingnag is pretty simple; he does not really understand the way the world works.  Gulliver says, 

[The king] wondered to hear me talk of such chargeable and extensive Wars; that, certainly we must be a quarrelsome People, or live among very bad Neighbours [....].  Above all, he was amazed to hear me talk of a mercenary standing Army in the Midst of Peace, and among a free People.  He said, if we were governed by our own Consent in the Persons of our Representatives, he could not imagine of whom we were afraid, or against whom we were to fight [...].

The king's criticism of a standing army is a popular theme in England during this era.  According to the notes for this section, Swift had taken an anti-army stance in some of his other writings, as had a number of other prominent writers.  Further, an argument in Utopia makes a similar argument, comparing mercenary soldiers to thieves.  
Further, Gulliver's offer to share the secrets of gunpowder with the king elicits harsh criticism.  He says,

The King was struck with Horror and the Description I had given of those terrible Engines, and the Proposal I had made.  He was amazed how so impotent and groveling an Insect as I (these were his Expressions) could entertain such inhuman ideas, and in so familiar a Manner as to appear wholly unmoved at all the Scenes of Blood and Desolation.

Such criticism, again pointing out how violent Gulliver's people are, cannot help but remind us of all the wars fought in England over politics, religion, territories, and so forth.  Their absolute willingness to use gunpowder, something the English also used extensively, further points the finger at England as the object of the king's criticism.