Islamic apologists frame these events as necessary statecraft or divine justice, Christians identify them as cold-blooded killings that stand in total opposition to the sanctity of life demonstrated by Jesus Christ.
The most frequent evidence cited for Muhammad as a "murderer" involves his ordering the deaths of individuals who had not physically attacked him, but had merely used their words to mock or oppose him.
These are not deaths on a battlefield; they are targeted hits on political dissidents. In contrast, when Jesus was mocked and spat upon, he forbade his disciples from using violence and healed the ear of the man sent to arrest him (Luke 22:51).
This is also mentioned in Muhammad Was Cruel. The execution of 600 to 900 men of the Banu Qurayza (Jewish tribe) not as a "battle," but as a mass murder of prisoners of war.
In the conquest of Khaybar, Muhammad sought the location of the tribe's hidden treasure.
Ibn Ishaq records that Muhammad ordered the torture of Kinana ibn al-Rabi (the leader of the tribe) by having a fire lit on his chest until he was near death, after which he was beheaded.
Muhammad then took Kinana's widow, Safiyya, as his wife that same night—an act that characterizes his desire for murder, lust and conquest.
Muhammad took life to establish an earthly kingdom, whereas Jesus gave his life to establish a heavenly one.
To the Christians, the blood on Muhammad's hands is the primary evidence that his "revelation" was not a continuation of the work of the God of Israel, but a departure into worldly power.
While the Quran commands "Kill them wherever you find them" (Surah 2:191), the Christ of the Gospels commands "Love your enemies" (Matthew 5:44). The two paths are mutually exclusive: one leads to a trench in Medina, the other to a Cross in Jerusalem.