I was, and am, under the impression that 'sin' was in the breach of the laws laid down (supposedly) by the God of the Christians as set out in the bible.
These laws have never, so far as I am aware, had any authority, in so far as it is possible, in this country (the U K), to be taken to either the criminal or the civil courts for breaching any of said God's laws.
Thus any 'sin' only has a value when committed by a committed Christian and, therefore, has absolutely no relevance to any or all non-Christians.
The only relevance that I can think that 'sin' might have had to a non-Christian was if they were charged with blasphemy, however on May 8, 2008, the Criminal Justice and Immigration Act 2008 abolished the common-law offences of blasphemy and blasphemous libel in England and Wales, with effect from 8 July 2008, so even that 'sin' no longer has any meaning for non-Christians.
This being the case I cannot see why any non-Christian, including myself, need waste another second in worrying about what any Christian, no matter how committed, thinks on the matter.
Basically sin has, to the non-Christian population, no relevenace whatsoever!
Except possibly the sin of putting water into a 21-year-old malt whiskey, and this 'sin' is usually only committed by Americans.