I suppose the distinction that might help us is between cultural advance and military capture of land, and this distinction is really not that tough to apply to history to extract moral conclusions.
If your religion wins my family's hearts and minds I have nothing to complain about, least of all "imperialism" -- but if your bishop (or Imam) rides and kills my kids and quarters horses in my living room -- you get the point.
I grant you your cultural factors; but the writer's point is that Islam's armies seized land, and European armies took it back. All the while, the eternal culture war of ideas waged, on its own battlefield, and largely irrelevant to this moral analysis.
Of course it can. Islam fundamentally spread by conquest.
The Arab Islamics began the rape, pillaging, massacres, forced conversions, head taxes, etc. with the prophet Mohammed, in the Arabian peninsula, as he massacred 600-900 Jewish men in cold-blood and his men raping and enslaving the women and children (Banu Qurayza, 627). This Jihad would extend throughout the Arabian peninsula (where under the second caliph in 640 the Jews and Christians were expelled from the peninsula), North Africa, Mesopotamia, Armenia, Persia, Syria, Palestine, South Spain before finally being stopped at Narbonne (720) and Poitiers (732). In the space of 100 years the Arab Islamics had massacred, conquered, dhimmiized, pillaged, whole INDIGENOUS Christian (non Arab) and Jewish communities. Bat Ye'or in, The Decline of Eastern Christianity under Islam (1996), at pp. 44ff. describes this blight on long-standing Christian and Jewish communities:
"After the death of the Prophet, the caliph Abu Bakr organized the invasion of Syria which Mohammed had already envisaged. He gathered tribes from the Hijaz, Najd, and Yemen and advised Abu Ubayda, in charge of operations in the Golan (Palestine), to plunder the countryside but, due to a lack of adequate weaponry, to refrain from attacking towns.2 Consequently, the whole Gaza region up to Cesarea was sacked and devastated in the campaign of 634. Four thousand Jewish, Christian, and Samaritan peasants who defended their land were massacred. The villages of the Negev were pillaged by Amr b. al-As, while the Arabs overran the countryside, cut communications, and made roads perilous. Towns such as Jerusalem, Gaza, Jaffa, Cesarea, Nablus, and Beth Shean were isolated and closed their gates (note: these towns had a majority Jewish/Christian (non Arab) populations). In his sermon on Christmas Day 634, the patriarch of Jerusalem, Sophronius, lamented over the impossibility of going on pilgrimage to Bethlehem as was the custom, because the Christians were forcibly kept in Jerusalem:"not detained by tangible bonds, but chained and nailed by fear of the Saracens [Arab Islamics]," whose "savage, barbarous and bloody sword" kept them locked up in the town.3
In Syria...Sophronius, in his sermon on the Day of Epiphany 636, bewailed the destruction of churches and monasteries, the sacked towns, the fields laid waste, the villages burned down by the nomads who were overrunning the country. In a letter the same year to Sergius, patriarch of Constantinople, he mentions the ravages wrought by the Arabs.4 Thousands of people perished in 639, victims of the famine and plague that resulted from these destructions..... Country areas, particularly the plains and valleys populated with hamlets and villages, were ravaged by Bedouins who set fire to crops, massacred and carried off the peasantry and their cattle, and left nothing but ruins. Townspeople were in a different position. Protected by their walls, they could defend themselves or negotiate the conditions of their surrender on payment of tribute to the Bedouin chiefs....
In fact, the record of the precise progress of the Arab conquests constituted a basic principle in the earliest stages of Muslim law, since it fixed not only the nature and taxation of the land, but also the legislation applicable to its indigenous inhabitants. Although some disparities appeared in respect of the towns, the majority of the villages fell into the category of conquest without a treaty. According to the strategy of jihad, the absence of a treaty allowed the massacre or enslavement of the conquered population and the division of their property.... Helped by local Arab support---particularly active in the central region and the lower Euphrates---and by troop reinforcements sent from Arabia, Muslims extended their raids on the countryside and villages to the south and center of Iraq around Mada'in (Ctesiphon).......they invaded the Sawad (Babylonia), the villages near the Tigris and Euphrates....These raids were supported by Umar who sent reinforcements from Medina.
The monasteries were pillaged, the monks killed, and Monophysite [Christian] Arabs massacred, enslaved, or Islamicized by force; in Elam the population was also decimated, and in Susa their notables were put to the sword.... Palestine was laid waste and plundered.13 The Arabs moved into Cilicia, taking inhabitants with them into captivity. Mu'awiya sent Habib b. Maslama to Armenia....On his orders, the population of Euchaita [Jews and non-Arab, i.e., Armenian Christians] (on the river Halys) was put to the sword; those who escaped were all taken into slavery.14 According to the Armenian chroniclers, the Arabs, after they decimated the populations in Assyria and forced large numbers of people to embrace Islam, "entered the district of Daron [south-west of lake Van] which they sacked, shedding rivers of blood. They exacted tribute and forced the women and children to be handed over to them."15 In 642 they took the town of Dvin and annihilated the population [mainly Assyrian Christians] by the sword.
Then "the Ishmaelites returned by the route whence they had come, carrying off in their wake a multitude of captives to the number of thirty-five thousand."16 The following year, according to the same chronicler, the Arabs again invaded Armenia, "wreaking havoc, ruin, and slavery."17 .... In North Africa, the Arabs took thousands of captives and accumulated a large stock of booty...."the Muslims set to work overrunning and laying waste the open country."19 Tripoli was ransacked in 643; Carthage was entirely razed to the ground and most of its inhabitants were killed [majority Christian]. The Arabs put the Maghreb to fire and sword, and it took them more than a century to restore peace there by crushing the Berber resistance....
The wars continued on land and sea with Mu'awiya's successors. Arab troops wrought havoc in Anatolia by numerous incursions; churches were desecrated and burned down; all the inhabitants of Pergamum, Sardes, and other towns were led into captivity. The Greek towns of Gangres and Nicae were destroyed. Contemporary Christian chronicles mention entire regions ravaged, villages razed to the ground, towns burned, pillaged and destroyed, while entire populations were enslaved. As has been mentioned, town populations were not always spared. They often suffered massacre or slavery, always accompanied by deportations. This was the fate of the Christians and Jews of Aleppo, Antioch, Ctesiphon, Euchaita, Constantia, Pathos (Cyprus), Pergamum, Sardes, Germanicea (Marash), and Samosata---to cite but a few examples. In the course of the Umayyads' last attempt to take Constantinople (717), the Arab army commanded by Maslama carried out a pincer movement by land and sea and laid waste the whole region around the capital."
That was just the first 100 years of the spread of Islam.