I do not understand why those missionaries make of Islam a threat? Why did they regard Islam as an enemy? Why did they talk and write about something was not there and why exaggeration? What did Islam and Muslims do to them?
Christopher Harrison very frankly and hatefully wrote about Islam in Africa as a "threat" to Christianity.
All the nations in Africa were living in peace and comfort till the establishments of colonies by western society, and the western society somehow was mislead by those missionary reports and did had many other intentions behind building colonies and occupying others lands. The effect of this historical event till now can be seen.

France and Islam in West Africa, 1860-1960, Christopher Harrison (1988: 31) quotes from Le Chaterlier and stated: “..In a later article Le Chaterlier warned of the great unity within the Muslim world….”

In his book , Edwin Munsell Bliss stated, “Islam. ” The great problem of African missions, is ”not the ignorance of its peoples, nor their fetich worship, not even the influence of un-Christian-Christian nations. All these are yielding more and more to the gospel. It is Islam…” (Bliss, The Missionary Enterprise 1908, p205)

I do not like to quote from the books, but everybody can read them and see what was going on then and how did they were planning and organizing conspiracy against Muslims and Islam and when we start to have a reaction and try to put an end to their deception and misleading they became angry and introduce themselves as innocent victim.