first, let me say that my take on religion is that it’s a crock. theology i can get behind, and understand, but religion is IMHO just stupid. that said, if you want to believe in a religion, that’s your call, and i won’t say anything bad about it. unless you try to convert me. then it’s open hunting season.
but more to the point. christians, and indeed any religious person who says LDing is a sin, is essentially saying that because of fear. fear and weakness. lucid dreaming can’t be a sin because, by definition, a sin is only commited when you do something that goes against the teachings of your faith. to the best of my knowledge, none of the major religions have done more than mention in some small passage the very existence of lucid dreaming, much less decried it as a sin. no, the reason for why someone would call lucid dreaming a sin is nothing more than fear.
the reason, you ask? simple. place a person in a world where he/she can do anything. literally anything. no laws, no boundaries, no nothing. the world is what you make of it. you could do whatever you wanted here. if you want, you could play god. or, you could just stand somewhere and pretend that everything is just normal. most people though, will do something that they want to do. eventually, they will be tempted to do something that goes against their faith. everyone has at one point or another wanted to do something that mommy or daddy told them not to, and this is the exact same thing. lucid dreaming is the ultimate temptation, the ultimate lure to commit any sin you want. those who know that they could never resist such a temptation will be quick to cry sin, in the hopes that the temptation will no longer exist. the weak shy away from their fears. the strong face them.
the point is, that only choices can be a sin. temptations are not. being tempted to kill someone is a temptation, but actually killing is the sin. temptations are neither sins nor virtues, and lucid dreaming is the strongest temptation in existence.
so in short, lucid dreaming is NOT a sin. period. end of discussion. what you do inside of a lucid dream though, is open to interpretation. personally i believe that no action in a lucid dream could be considered a sin, because to me at least, a sin requires something negative to happen to someone. it needs a victim, so to speak. and since there is no victim to anything you do in a lucid dream, i can’t see a reason for why any choice you make in an LD to be considered a sin. but that, however, is an entirely different discussion.