Thanks everyone for your perspectives.
I agree about not blindfolding children. I'm not proposing to not tell him about pirates, guns, or anything else that comes up, just not glorifying it.
I am very open with him about anything he asks questions about, anything that he is introduced to.
I object to the way they are introduced, not that he might find out about them.
I'm no pirate expert lol, in fact I know very little about them, but enough to know that they aren't/weren't nice people and I don't want DS aspiring to be one.

I hope that makes sense, I'm posting from my tablet.

ETA- We don't tell him fairies/ Santa/ Easter bunny etc are real either though. Santa is a game we play - Christmas for us is a (non religious) time to be with family and friends, Easter bunny is the same, fairies are presented as " oh look! She's dressed up as a fairy!" Rather than "look a fairy!" We still have fantasy, but he knows its pretend itms.
I guess this ties in with the pirate thing as they ARE real, but not the same as they can be portrayed. It makes it harder to explain...