I read an article a while back tracing the relatively positive attitude towards piracy in Ancient Greece to the increasing hostility towards piracy in later years. Fascinating stuff - robbing and enslaving people on the high seas is honest work, but trading goods between societies for profit is a filthy, lowdown, good-for-nothing occupation!
As I understand the hostility towards merchants, it essentially stemmed from a one-sided view of their behaviour:
The king (or Duke or whoever) demands taxes in coin, so you need coin. Up pops a merchant offering to buy your surplus grain, but trying to haggle the price down to as little coin as possible.
You have to find some buyer so you can afford the tax, and the merchant exploits that necessity. To afford the tax, you may end up having to work more so you can sell more. But then a bad year rolls around, you struggle to survive at all, and to add insult to injury that merchant is offering to sell you some of the grain you need… for much more than he last bought some from you, carving a profit out of your misery.
Of course, from a modern perspective we can see that the merchant is an important logistical service provider to feed the city folk that do non-agricultural labour (some of which may circle back to benefit the farmers, like ploughs), the profit essentially being a wage for that service, and the real vampire are the aristocrats that grow rich off that circle of exploitation.
But as farmer, you don’t see the king get richer. There’s no newsfeed showing pictures of the grand new mansion he built himself. You see the merchant trying to squeeze you for as much as possible, and you hate him for being a leech.
I’m guessing most of the inland farmers holding those views had less contact with the pirates, but also, if using force to take what you want is normalised anyway because there’s another war rolling past every few generations (if not more frequently, depending on where you live), piracy may seem less “wrong” too.
And that’s different from today, how?