Brother H2O, you made very good points and Qur'anic quotes. Also, it is obvious indeed they blow words out of mouth in one breath, without knowledge. Here are a few quotes on history of Spain, not from Islamic sources. Apparently there's more to the issue than the simple-minded conclusion that it is an invasion.
http://www.answers.com/topic/history-of-spain
A raiding party led by Tariq ibn-Ziyad was sent to intervene in a civil war in the Visigothic kingdoms in Iberia. Crossing the Strait of Gibraltar, it won a decisive victory in the summer of 711 when the Visigoth king Roderic was defeated and killed on July 19th at the Battle of Guadalete.
http://xenohistorian.faithweb.com/europe/eu06.html
By 708 the Islamic conquest of Morocco was complete, and a series of dumb acts on the part of the Visigoths made sure that their worst nightmares would come true. First, the Visigoth king, a religious moderate named Witiza, died in 710. His son Womba wasn't anti-Semitic enough to suit the Church, so it backed Roderick, the duke of Baetica, and Roderick took the throne instead. In response to this coup, Roderick's enemies and Womba's friends got together, and invited the Moslems to come to Spain; one of them, Count Julian of Ceuta, even provided ships for the crossing.
http://www.newadvent.org/cathen/14169b.htm (Legend?)
Legend has it that Count Julian, the governor of Ceuta, in revenge for the violation of his daughter, Florinda (Also called La Cara), by King Roderic, invited the Moslems and opened to them the gates of the Peninsula.