Q. Why do you worship idols?
A. We don’t worship idols. Idolatry is the worship of an imagined form of God.
Deity worship is not idol worship but is worship of the Lord according to His instructions.It is an incarnation of the Lord just like many other incarnations like Lord Nrisimhadev,Lord Vamana & Lord Ramchandra.
God is spirit but as Krishna reveals in the Bhagavad-gita, matter is His energy. Because we cannot perceive spirit in our present condition, Krishna allows us to see Him in His Deity form made of material elements. He tells us that the Deity installed according to the directions of the scriptures is identical to Him.Whatever service we offer to the deity,Krishna directly accepts it.There are several instances in the past where Krishna in His deity form has reciprocrated with His loving devotees.
But to realize that there is no difference between Krishna and His deity form,we need to purify our senses.We need to have a pure heart.And the most powerful way to do this ,according to the scriptures, is to chant and attentively hear the holy name of the Lord:
Hare Krishna Hare Krishna Krishna Krishna Hare Hare
Hare Rama Hare Rama Rama Rama Hare Hare