Large scale international IP Treaties weren't really a thing until the near the end of the the 19th century, so "theft" isn't really the correct term when there were no agreements or laws governing trans-national IP rights.
Those agreements really only got started with the Berne Convention-- mainly creative works-- and the Paris Convention-- basically industrial patents. (Yes there were some other smaller agreements before, but these brought things into much larger scale with many, many more signatories to the agreements)
Besides, your line of reasoning amounts to "Other people got away with bad things so it's not fair that I do to" As a parent, I spot that line of logic often in with my kids, and it doesn't hold together very well there either.
Those agreements really only got started with the Berne Convention-- mainly creative works-- and the Paris Convention-- basically industrial patents. (Yes there were some other smaller agreements before, but these brought things into much larger scale with many, many more signatories to the agreements)
Besides, your line of reasoning amounts to "Other people got away with bad things so it's not fair that I do to" As a parent, I spot that line of logic often in with my kids, and it doesn't hold together very well there either.