Finally, a non-believer asks a good and pertinent question that gets to the crux of the issue. I've answered this previously in God related threads, but will do so again.
God could destroy Satan at any time he so desires, but with God created spirit sons and humankind able to know of God's reaction to Satan's challenge of universal sovereignty, for God to immediately destroy Satan would leave the question of who is the rightful sovereign of the universe unanswered, and thus leaving God's position questionable. (Answering this question is the main point of the bible). So, in answer to Satan's challenge, God has allowed Satan a period of time to rule over the earth. With God having created humankind in a state of sinless perfection, and Satan's convincing of Eve to go against God's orders, sin was introduced into the world by Satan's actions. How this relates to the issue of universal sovereignty is how by Satan's actions and under Satan's rulership the earth and all the wickedness that's occurred is all on Satan's watch. Thus God allowing what's occurring on earth at present is proving a point to all as to whom has the right to rule and make a better universal sovereign. Either it be God and his desire for humankind who originally had sinless perfection and has promised in the bible to return faithful humankind to such a state once He calls time on Satan's period of rulership over the earth; or Satan, and we've seen during our lifetime and by means of history books the anguish, misery and death that by means of his actions he has wrought onto humankind during his rule.
Satan and the rebellious spirit beings who followed him have contempt for humankind and know they have only a limited period of time before God calls time on Satan's rulership. Thus in Satan's great anger, knowing his limited time before God finally does away with him, is attempting to drag down with him as many people as possible by turning folks against God, thus making these ones worthy of destruction at God's hand when execution of judgement on Satan's corrupted system and peoples is carried out at what the bible refers to as Armageddon.
Umm no that is a complete load of rubbish, Satan's existence is what makes people question gods reign at a basic level.
If Satan did not exist then there would be no question between them.
Who is your father? You know your father he raised you, you've only ever known him as your father.
Who your father is, is not questionable.
But if another dude shows up claiming to be your father, that calls into question wether your father is actually your father.
If the other guy didn't exist it would never be questioned.
The comparison to "Satan" is very much the same. Rather then legitimise god's rule Satans very existence calls it into question.
Your notion's on "legitimacy" are more reflective with how monarchies used to claim "legitimacy" see: killing there opponent's.
Remember: war doesn't decide who is right only who is left.
The ability to kill another being doesn't prove your right it only silences your critics.
Fact is we're supposed to believe that an all knowing being created other beings knowing they would rebel and lead other beings to rebel and then twist and corrupt, the all knowing beings "greatest creation", all so at some stage down the track this all knowing being and murder (and murder is completely accurate all of this is pre meditated) the **** out everyone who rebelled or got corrupted.
And this is the real crux of the issue. If "God" is omnipotent then he is responsible for everything, there is no issue which he is ignorant of. By definition there cannot be, therefore there is no "test" God knows in advance who will pass and fail his "tests" even before creating them, even what Satan would do. Literally everything.
Now by any sane rationalisation this whole thing is an utterly cruel exercise and unnecessary exercise, if you know the results of your "test" a test which no less results in the slaughter of billions. Why would you go through with it?
We're left with two equally disturbing outcomes either "God"
is sadistic, by an measure of the word.
Or he's not actually sure of the outcome.
The first questions just how much he "loves" people
The second questions wether he's actually omnipotent at all.
Both outcomes question his relationship with people, fact is God cannot be a "loving" God and omnipotent, no one who truly loves someone would put a loved one truth such a test, particularly if they knew the outcome in advance.