system
Given the following post, respond as if you're commenting on Reddit:
human
I believe murder is justifiable if there are no possible negative effects on society. CMV

First of all, please note that my argument is purely theoretical, due to the fact that the positives and negatives of any action are never clear. I would never condone murder, simply because it cannot be known if any negative effects are to follow.

That being said, I would like to construct a possible scenario. There exists a homeless person in a major city; this person has no friends, no family alive, and nobody depends on this person or cares for this person. This person does nothing to contribute to society or any individual, he merely exists. Given this situation, I would think that the murder of this person is entirely justifiable, based on the idea that his/her death will have no negative effects on any person or on society.

I don't even see this as a negative for the person- if the death is instant and painless the person will never even know what happened. In death you can't bemoan your lack of life or regret the things you never did, because you're dead. So I don't see this as a negative for the individual in question. Another issue: what if this person had gone on to make a positive impact on society in the future? I think it's equally likely that this person could have gone on to make a negative impact on society, in which case you would be doing the world a favor. I get that murder is simply morally wrong to basically everybody, but logically I see nothing wrong with the murder of the individual I've described.

Just to clarify, I really don't mean for this to sound cold-blooded. When I've brought this up to friends they've mostly just responded with disgust or disapproval. However, nobody has really offered a counterargument to my view. So, CMV.
gpt
There are two separate threads of logic going on here.

thread 1:
If no one is affected by this person's death then this person doesn't matter

thread 2:  This person doesn't matter to themself.

Thread 2 is completely indefensible.  People who think like this kill themselves.  Therefore for any person who has not yet killed themself, the odds are statistically speaking extremely high that they do not want to kill themself.  Who are you (or who is any theoretical killer) to decide for them?  If it doesn't matter what **their** wishes are, then there is not even a reason to consider [thread 1] because you have already decided that what people's wishes are are irrelevant when you decide that a person's wish to live is irrelevant.  Then what you are left with is the postulate that it is okay to kill any person at any time, no matter who is affected because people's wishes are irrelevant.

Besides that, you have no way to know if there is or is not a afterlife.  You can't definitively say whether or not dead people have an opportunity to bemoan their lack of life.