I'm not sure how it's possible to argue that abstaining from something can be a sin, unless we're talking refusal to take the Eucharist or something.
I don't see how refusing to take communion could be a sin unless it was done with the reasoning of refusing to take it from a woman or something. The far more common belief is that it would be a sin to take it under some circumstances (which I don't agree with.) But I know that I would be very uncomfortable taking communion in a Catholic church even if the church's rules on it didn't "prohibit" me for example. I also wouldn't hold anything against someone who wasn't Christian declining to take communion even if the church they were visiting was OK with it.
What I think is wrong and could be a sin would be encouraging ("threatening" might be a better word in some contexts) someone to not take in communion because of some sin they had committed like the Catholic Church and some evangelical ones do. I kind of think discouraging alcohol consumption is sort of similar. It's not an issue if you are a designated driver, or get sick off it easily, or just don't feel like drinking that night or at all. But the legalistic prohibition many churches have on alcohol is wrong, and someone abstaining for that reason alone is kind of in the same vein as "ex-gay" "therapy". Not saying that it's anywhere near as damaging of course, and "sin" might be too strong of a description, but it's definitely not the right thing to promote.
Also I'm so irritated by the US's stupid laws on alcohol and current drinking age despite being legal for quite awhile now that I kind of hold that it's an unjust law worthy of civil disobedience and someone declining to drink for no reason other than they they are not above the legal age is not quite a "sin", but also certainly not the right thing either. Mind you this is extremely rare anyway.
Poll
