First, it was not the first time European Christian soldiers fought Islamic opponents, as that was begun by the Almoravid invasion of Spain in the eighth century and continued well past the crusades. The Iberian conflict influenced Europe in significant ways, but it was not an overwhelming obsession, showing that Europe as a whole was not driven by any sort of desire to stamp out Islam as a rival religion.
The second problem with portraying the crusades as the beginning of religious animosity between Islam and Christianity is that this view puts the motivation of the war squarely in the differences in the two belief systems. When looking at the writings of the day, men like Pope Urban and Bernard never refer to any specific belief espoused by Islam, simply labeling their enemies as pagans or infidels. It is important that this point is emphasized. At no time did any Pope in the decades prior to the crusade, or even Bernard after the crusade, focus their energy on the Muslim nations."
"... The specifics of the Islamic religion was not the reason behind their attacks, but rather the simple fact that they were not Christian, thus fighting them was not seen in the same way as fighting and killing fellow Christians. This may seem like a rather self-serving idea, but it was a simple way to mitigate violence between the people of the church, tell them to fight those not under the protection of God. This is a callous turn of phrase, but it does emphasize that the target of the crusades was not chosen for their specific religious beliefs, but rather that they simply were not Christian, which shows the focus of the crusade was not an anti-Muslim holy war, but a move to stop violence between Christians."
source text: "Bernard of Clairvaux and the Knights Templar: The New Knighthood as a Solution to Violence in Christianity" by Boysel (2009); illustration source