It's certainly that the Arabic empire waxed and waned in power over the centuries but they conquered nearly all the territories that are still Arab today in the first century off their existence. In the same manner that America conquered nearly all it's territory in its first century.
The fact that the Arabic empires waned afterwards yet managed to ensure that their conquered territories would still continue to the use the Arabic language and adopt their religion in spite of the absence of modern bureaucracy illustrates the degree to which the actions that lead to those results had to be deliberate.
Not even the Persians, the Hellenistic kingdoms, the Mongols, or even the Romans had such a long lasting impact on the Middle East. The Caliphates did not accomplish those things purely out of habit but consciously as a matter of strategic policy.
I would, of course, agree with the idea that the Arabic empires were equal opportunity conquerors just like everyone else and had no unique level of animosity towards the Christian kingdoms. They, after all, went after the Sassanids with the same degree of vigor.