Quote 1
"Heard of [Captain Flint]!" cried the squire. "Heard of him, you say! He was the bloodthirstiest buccaneer that sailed. Blackbeard was a child to Flint. The Spaniards were so prodigiously afraid of him that, I tell you, sir, I was sometimes proud he was an Englishman." (6.22)
One odd historical detail of piracy in the 17th and 18th centuries is that, far from being outside the law, pirates were often secretly sponsored by governments of opposing European powers. So English pirates would board Spanish, French, and Dutch ships in the hopes of ruining their foreign trade. This is why a rabid patriot like Squire Trelawney can admit to admiring a pirate like Captain Flint.
Quote 2
"Most likely Trelawney's own men," said the doctor; "those he had picked up for himself before he lit on Silver."
"Nay," replied the squire. "Hands was one of mine."
"I did think I could have trusted Hands," added the captain.
"And to think that they're all Englishmen!" broke out the squire. "Sir, I could find it in my heart to blow the ship up." (12.37-40)
Squire Trelawney's patriotism blinds his judgment. When Long John Silver tells Trelawney that he lost his leg in a battle under Admiral Hawke, Trelawney believes him. Here Squire Trelawney is disappointed in the pirates not just because they want to murder him, but because they are all Englishmen. Squire Trelawney's idealism makes him an easy mark for Long John Silver, which is perhaps meant to be a jab against idealism.