Why is idolatry bad?

If Israel is any representative of humanity, Jeremiah had painted a grim picture of human nature. Whenever chances arise, man rebels.
Many a philosopher is optimistic about human nature. They believe that man is intrinsically good. They exhibit very noble qualities: compassion, reason and perseverance. Yet, man can be as ferocious as wild animals, lustful and greedy beyond mere survival.
As a teacher, I share the conviction with these optimistic philosophers. This is a conviction and therefore it cannot be logically proved or disproved. Had I believed otherwise, it would have defeated my whole career as a teacher. What's the point of engaging your whole life in and out of the classroom with students?
I think God also shares our conviction. Otherwise, God would not have intervened actively in human history. He has chosen to reveal Himself through interactions with Israel. It all began with the historical event of Exodus. From Egyptian bondage, God delivered them and brought them into a land flowing with milk and honey. He actively cleared up the land of other tribes to make it an inheritance for Israel.
Israel was holy to the LORD, the first fruits of his harvest.
All who ate of it became guilty; evil came upon them, says the LORD (Jeremiah 2:3).
When life prospered, Israel began to stray away from God. They fell into the idolatry.
And I brought you into a plentiful land to enjoy its fruits and its good things.
But when you came in you defiled my land, and made my heritage an abomination.
The priests did not say, 'Where is the LORD?' Those who handle the law did not know me;
the rulers transgressed against me; the prophets prophesied by Baal, and went after things that do not profit (Jeremiah 2:7-8).
Has a nation changed its gods, even though they are no gods?
But my people have changed their glory for that which does not profit (Jeremiah 2:11).
Yet I planted you a choice vine, wholly of pure seed.
How then have you turned degenerate and become a wild vine? (Jeremiah 2:21)
The last quotation echoes Isaiah's famous vineyard song (Isaiah 5:1-7).
As a Chosen People, Israel had fared poorly. She did not live up to the expectations of God. In Judaism-Christianity terms, she worshipped idols. She had committed adultery against God.

Idolatry clouds understanding and true knowledge (of Yahweh). But why do people fall in love with idolatry? Why do they choose to enjoy second-rate religion instead? Can laziness explain it? Can false security explain it? I think security does.
We Chinese are a very pragmatic people. (Of course, I risk over-generalization when I make such a claim. It is as elusive as a multi-disciplinary study of Chinese Personality and draw conclusion on the most obvious. Chinese are hard-working. They are addicted to gambling. They care more about their own families than their community and country. They are idolatrous etc.) They are willing to pay tribute to (worship) whatever gods or goddesses that prevent evils and bring fortunes. Only a few philosophically elitist scholars would venture into the realm of the absolute and the transcendent. Most folk are very ordinary and down to earth. Dealing with gods is no different from dealing with human trading partners. So long as it brings benefits, we have no qualm seeking it. The late Chinese Communist patriarch Deng Xiao-ping made it crystal clear: No matter whether you are a white cat or a black cat, so long as you catch rats, you are a good cat! So, if Deng Xiao-ping is any representative, for us Chinese, whether you are Sakyamuni or Yahweh, so long as you prevent evil and bring fortune, you are a good God! Performance counts. In view of so many gods and goddesses worshipped by Chinese, we are truly pragmatic! No wonder Yahweh did not choose Chinese as the Chosen People.
From the criteria of Truth, Goodness and Beauty, idolatry fails at least two of them.
Firstly, idols are man-made and not real. In a sense, idol-worshipping is in fact a self-worshipping. Idolaters worship their own creation, worship themselves. As the Psalmist says,
They have mouths but do not speak; eyes but do not see (Psalm 115:5, 135:16).
Secondly, men mistakenly attribute to them goodness which comes from God. It is a lack of understanding of true knowledge on the part of idolaters.
O Ephraim, what have I to do with idols? It is I who answer and look after you. I am like an evergreen cypress, from me comes your fruit (Hosea 14:8).
Lastly, I am not an aesthetic and am not able to pass judgment on the artistic creations inspired by idol-worshipping. All in all, I cannot pass a judgment favourable to idolatry. It is a waste of resources, like my students who waste their time playing online games, dating and fooling around. They are not even pragmatic!

My dear Advocate, if we do not learn the lessons from the Israelites, it is our fault. You have set before us the path of life and the path of desolation. It is our fault to choose the latter. I pray that we hold on our faith in You, though we do not see You, see immediately Your work. I also pray for my students so that they come to their senses and do not waste the talents and potentials You have bestowed on them. Amen.