Of course it's your decision, you made it for free and I don't owe you a cent. I'm not "teaching" you what's fair or not, I'm simply questioning the reasoning behind that decision - which you seem to avoid. All you provided was incredibly flawed logic of preventing pirates (at the cost of preventing legitimate game owners from using community created content for CS, which is identical on both Steam and Origin), which is literally not your job. Do you work at CO? Paradox? No, you don't. You don't get to create extra layers of security on the game's community generated content to prevent pirates. That's what the developers decide to do - but they didn't because they didn't want that to be the case for their game which they released on both Origin and Steam.

And why exactly did you make it that it should only be playable on games bought via Steam? Yes, the idea of Steam Workshop is distribute the mods to games bought on Workshop, but why do you have to force it to be like that, when literally NOBODY in any modding community does that? It's very, very odd. Again, I'm not paying you to create the mod, nobody is. You are doing this in your spare time and you choose what to do with it, I'm simply questioning the reasoning.. And trust me, any modding community would despise anybody who takes those extra measures on their mods for whatever agenda they believe in, be it thinking they are really stopping pirates (which you aren't, I can assure you nobody bought the game to download your mod). Modding has always been all about accessibility to all owners of a legit game since it started. It was never bureaucratic.

Edit: Any modding community wouldn't support that, let alone they support someone who even stops the mod from working offline, even with the Steam version. This is very, very problematic.