The rock that the Moslems pray to (even though they don't believe in idols...) was in fact first used for Pagan worship and is a black meteorite.
Becuase of this stones relevance to all Arabic peoples different Pagan religions at the time, it was seen as a unifying symbol and was incorporated into the new religion and political system which aimed to unify the Arab people.
You keep reading way too much ignorance from non-muslim sources.
The Black Stone, in Muslim belief, originated in the time of Adam. According to the Hadith, "it descended from Paradise whiter than milk, but the sins of the sons of Adam made it black". According to belief, an angel spoke to the prophet Abraham, and told him to institute the rite of the stone in the hajj at Mecca.
We do not worship this stone it's a meteorite:
Islamic tradition holds that the Stone fell from Heaven to show Adam and Eve where to build an altar, which became the first temple on Earth. Muslims believe that the stone was originally pure and dazzling white, but has since turned black because of the sins of the people.
Adam's altar and the stone were said to have been lost during Noah's Flood and forgotten. Ibrahim was said to have later found the Black Stone at the original site of Adam's altar when the angel Jibrail revealed it to him. Ibrahim ordered his son Ismael—who is an ancestor of Muhammad—to build a new temple, the Kaaba, in which to embed the Stone.
As Umar ibn al khattab is quoted in a hadith, speaking about the stone, you can not benefit me or harm me. In other words it is not a part of worship nor a 'deity' idol.