The Bible also opposes idolatry, even though the prophets say that an idol is nothing but a thing made out of wood and precious metal.
as Psalm 135 says:
The idols of the nations are silver and gold,
made by the hands of men.
16 They have mouths, but cannot speak,
eyes, but they cannot see;
17 they have ears, but cannot hear,
nor is there breath in their mouths.
18 Those who make them will be like them,
and so will all who trust in them.
Or as Jeremiah says,
People who worship idols are stupid and foolish.
The things they worship are made of wood!
Any quick concordance search will show that "worthless" and "idols" show up a lot! So, if there is no power in an idol, why does God make such a big deal over it? Because of it's effect on the idol worshiper!
The problem with magic isn't so much the "magic," but rather the senseless chasing after another power. When, in Acts 8, Simon the magician wanted to purchase this power, Peters reaction was that he didn't understand what God was.
As Luke writes it in Acts,
9 Now for some time a man named Simon had practiced sorcery in the city and amazed all the people of Samaria. He boasted that he was someone great, 10 and all the people, both high and low, gave him their attention and exclaimed, “This man is rightly called the Great Power of God.” 11 They followed him because he had amazed them for a long time with his sorcery. 12 But when they believed Philip as he proclaimed the good news of the kingdom of God and the name of Jesus Christ, they were baptized, both men and women. 13 Simon himself believed and was baptized. And he followed Philip everywhere, astonished by the great signs and miracles he saw ...
18 When Simon saw that the Spirit was given at the laying on of the apostles’ hands, he offered them money 19 and said, “Give me also this ability so that everyone on whom I lay my hands may receive the Holy Spirit.
20 Peter answered: “May your money perish with you, because you thought you could buy the gift of God with money! 21 You have no part or share in this ministry, because your heart is not right before God. 22 Repent of this wickedness and pray to the Lord in the hope that he may forgive you for having such a thought in your heart. 23 For I see that you are full of bitterness and captive to sin
To this same end, magic is not an opposing force to God, but is rather a red herring that keeps them from Him.