No, it isn't that difficult. It only becomes difficult if a person is FORCED to consider it in a philosophical vacuum, by wrenching what seem to be problematic concepts from their narrative and/or historical context. This contortion of logic is not much different that what illusionists do with their slight of hand on the stage. They are successful when they get the audience to make certain assumptions about what they think they are seeing.
So, in essence, IF some being showed up, and I had had absolutely no contact with that same being previously, and that being claimed to be God, and it asked me to kill (or even murder), THEN, no I would not.
Again, as a Christian, I can conclude that this kind of thing IS NOT going to happen, and I can do this since I take the entire Bible as my contextual basis for contemplation. So, if Krishna showed up and asked me to kill my cousins, I wouldn't feel compelled to do so, since I'm a Christian.
Peace