Posting with the username "Dictionary", gordo says:
As a first stop off, I therefore suggest you work your way through the Blue-Letter Bible Don Stewart FAQ here, and in particular on the matter in question from you, the set of questions on Angelology. (the word "here" is a link to this):
Rule of thumb: the Christian Faith has been around for some 2,000 years, and has always had in it men of the top rank of intellectual capacity, while being challenged on many points by critics and worse than critics. So, regardless of whether or no the particular Christian in front of you has a good answer to a question you raise just now, there will as a rule be a serious answer to the question. So, do some research.
The FAQ in question answers on the subject of Evil Angels, beginning:
Who Are the Evil Angels?
The beings whom we now call “evil angels” were part of God’s original creation of spirit-beings. Though they were originally created as sinless, holy beings, these angels decided to rebel against God.
Power Of Choice
The evil angels, like the good ones, were all given the power of choice or moral judgment. They were placed under a period of probation where they could decide whom they would follow.
[I add: they were created as moral beings, with the power to love, which requires the power of choice. In exercising that, they chose instead the way of selfishness . . . thus evil. And, the onward issue of evil is best looked at through Plantinga's Free Will Defense, on which I have previously linked. Kindly, do not allow yourself to be distracted by rhetorical rebuttals that confuse a defense with a theodicy. A defense shows logical coherence and has no need to assert premises that skeptical objectors will be inclined to accept. It turns out that on augmentation with a logically possible state of affairs across possible worlds, the theistic set of propositions is demonstrably coherent. On the related inductive forms of the problem, the pivot turns on the issue I have again raised yesterday: the core gospel issue [at this point the issue is specific to the Christian faith], and the power of redemptive trinitarian monotheism to resolve the philosophical problem of the one and the many comes into play. Bottomline, there is no good reason to reject the contention that a world in which virtue is possible and the required free creatures on balance do more good than ill, has a greater good-making potential than a programmed world in which there is no true freedom, so no virtue. But getting to that bottomline requires some pretty serious thought.]
Left Their Rightful Place
Under the leadership of Satan, certain angels sinned and left their rightful place. The sin of these evil angels was their revolt against the Lord and His commandments. The Bible says.
And the angels who did not keep their own position, but left their proper dwelling, He has kept in eternal chains in deepest darkness for the judgment of the great Day (Jude 6).
They left their proper habitation – the reason for which they were created. When they chose to do this and sin against God, it was at that point they became evil angels. They were not created as evil beings . . .
I don't know about any of you but I just hate it when angels go bad. satan must have a better sales pitch than god.
Hmm, angels on probation. Makes perfect sense. LMAO! Is gordo crazy, or what?! He wouldn't know a "pretty serious thought" even if one were to hit him with the force of a super nova.