It depends on what sin means. If it's something that offends God, well then it offends someone and if I'm in my right mind I don't do it. It's hurting someone, even if only emotionally. I shouldn't care if that person is despicable. I don't want to be despicable. It's like the dreadlocks thing. Nobody is saying you shouldn't have the legal right to wear your hair however, but if it's bothering somebody, the right way to handle that is not to do it. It doesn't matter if they have a good reason. It doesn't matter if they're correct that they invented it. It bothers somebody, don't do it, that's the end of it.
In the context of the question, Christianity is true and God exists, so somebody is bothered by this action. He tells me about it, I will try not to do it. Sending me to Hell for it is merely despicable on his part, but I don't think I should care. I don't think me being decent has too much to do with the decency of the person I'm being decent to. If the restriction is crippling, I may deeply wish that I lived among people who weren't always so bothered by everything. I may even resent them. Hate them, even. I'll even realise that I could have that thing I want if he just stopped using omniscience to peep at me, and he could not be bothered. But I can't control what others do. I can only control what I do.
I used to live in a place where up to 10 female chickens were legal and I wanted them. However, someone was bothered so I didn't have any. When I was younger, I saw her constant calling of the police and reporting and reporting and reporting (someone else who had a few hens) until this person got rid of the chickens, as being an insufferable busybody and power-tripper, and wrong, and someone who should just go away. Now I look at that behaviour equally sadly, but because I think, people shouldn't have to do that.
And if sin is something more real and means that I'm (even if indirectly) hurting other people, and that's why he is bothered, then the case is even better that I should want to know about it and shouldn't do it.