If you think God does not exist, you are right. As per the Vedanta, God does not exist. It is only Brahman which is the base of life and universe. The nearest thing to God is probably the space or ether which supports the universe.
When He has no form, desire, ego or any qualities of His own, how can anyone become devoted to Him? However, He is supposed to be within us all. The whole universe is His creation. When we talk of Love for Him, we talk of Love for his creation. A lady had once approached a Swami and asked him how she should love God when she knows nothing about Him.
The Swami asked her if there is any one whom she loves. She said she loved her grandson. The Swami told her she should consider her grandson as a gift from God and bestow her love on him and God will get that love.
The grosser a man, the bigger proof he needs for His existence. Someone needs a scenario like Mount Everest to marvel about Him, but others who are more subtle and sensitive get impressed just by seeing a pomegranate so nicely packed with seeds as God’s most wonderful creation. Similarly, a Bhakta sees His image in His statue.
Not that the statue is the God. We see India in our flag but the flag does not become India. We see marriage in a marriage ring but marriage does not get nullified if the ring is lost. Similarly, we have God or Brahman. He does not cease to exist if images are not there.
Like in Sankhya Yoga or Gyan Marg, logic plays an important part but the same logic you cannot apply in Bhakti Marg. But one thing is sure: If one is really devoted to the Lord, his actions get dedicated to the Lord and he would find it difficult to harm others. It is easier for a Bhakta to become a Karam Yogi.
The best way is to choose a path which suits you and let others choose their own.