Isn't that like worshipping an idol?
Muslims do not worship the black stone. They regard the stone as a created thing. The most fundamental principle of Islam is that nothing or no one is to be worshipped except Allah, the one true God.
Muslims who can afford the journey are required once in their lifetime to visit the House of Worship in Makkah. This was the first house built for the worship of the one true God. It was constructed by Abraham and his son Ishmael, peace be upon them. The black stone was brought to them from heaven by the angel Gabriel to function as a corner stone. It was thus affixed in one corner.
Because Muslims kiss that stone, some observers hastily conclude that Muslims worship it. A kiss, however, is not an act of worship unless it is accompanied by an intention to worship. If you kiss your child, for instance, that does not mean you worship your child.
Some may find it strange that Muslims should treat a stone with respect. But this is not just any old stone. It is an item out of paradise.
The act of fixing a stone to mark a place of worship is as old as history. In the Bible we are told that Jacob, on whom be peace, had fixed a stone at a place where he saw a vision. He poured oil on it and called it Bethel meaning 'house of God' (see Genesis 28:18). He did this again upon God's instruction (see Genesis 35:1, 14, 15). No one should understand from this that God instructed Jacob to worship the stone.