I think this question is easily solved when you examine the assumption behind the objection.
The assumption seems to be that the devil ultimately impedes human fulfillment. The devil doesn’t do this: the devil doesn’t “send” anyone to hell.
The article you site says:
Satan will tempt the humans into sinning, do a bunch of evil, and try to steal their souls.
The devil doesn’t steal souls. Does the work to lead others astray? Yes. But any individual person in hell is there because of that person’s free consent. Any “temptation,” actually, lessens culpability; temptations – or anything that tends one toward an objectively evil act (such as emotions/passions, personality, addictions) – affects the freedom of an individual. Traditional Catholic moral theology would say that one cannot commit such a mortal sin unless the person commits the act with full knowledge and freedom.
Whether or not the fallen angels fell would have no bearing on the fact that sin is within the will.
So then what about the alleged physical evils caused by the devil?
First off, it would seem much of the “physical evil” in the Universe is built within the very fabric of the Universe: The world is finite; earthquakes and sickness are not seen as coming from the devil per se. So the question really is the problem of evil and suffering in general.
The gist of it all boils down to this selection from the article:
If God knew Satan would become evil, and chose to create him anyway (as opposed to skipping him and creating a different angel, or creating him with different desires, or not creating anything at all), God is responsible for the consequences.
Well, God *is *responsible for the consequences of Satan… but in what sense? Only this: That God, the source of all beings – He Who Is BEING itself – sustains the Devil, a free creature, and his existence. But as a free creature, the devil is culpable for the free, evil acts he commits. Not God.