What source says that? Every source I'm familiar with says when he returned to Mecca (after winning the war) he entered peacefully and harmed no one, but went to the Kabba and destroyed the idols there.
I mean, I agree with your overall thesis (he did have to fight a war to reach Mecca, though the Meccans attacked him in Medina first), but this seems to go beyond what I've heard before, and I'm curious where you found it.
In Christ,
Macarius
The Sword of the Prophet by Serge Trifkovic
For instance,
"Only fighting the despised Meccans would satisfy the desire for revenge of true believers who were slighted and persecuted by the haughty merchants" p35
So he started raids on Meccan merchants, and eventually became successful, launching his first successful raid against them in Ramadan, taking them by surprise. God had just conveniently given a revelation that raids were allowed in Ramadan, how lucky for Muhammad! Raids continued, growing into battles, even though " It was most unusual for an Arab to go so far in his estrangement from his tribe as Muhammad had done even before Badr; to take arms against his kinsmen was unprecedented...divine justification was required for so radical a step as ambushing and murdering one's own kin." Again, lucky for the religion of peace, "Allah's messages, conveyed by Muhammed, grew accordingly more bellicose:" I will strike terror, etc etc, smite them, etc" p 36
Allah also conveniently made booty and ransom lawful and good at this point, and when a dispute arose over division of the spoils, Allah told Muhammed that he should take the whole lot. p37
Now where do you find that the Meccans attacked him in Medina first? That contradicts everything in here.
Anyway, Muhammad dealt very harshly with his prisoners, beheading them all, (hmm, that sounds familiar). Then he "returned to Medina in triumph and proceeded to settle scores with his detractors there. An atmosphere of fear descended on the city; informers all disrespectful or merely careless remarks to the prophet, who followed them up with "proceedings that were sometimes both cruel and unscrupulous". ...The options for all Medinans were reduced to conversion, expulsion, or death." p38-39
and on and on. p 39 gives examples of two political murders 2 poets who spoke out against him were murdered by his followers, although "that a person of so advanced an age should be murdered for a verbal slight would have been inconceivable to the pre-Islamic Arab custom."
There's a lot more, truly horrifying stuff. That such a religion could be called the Religion of Peace, or put on the same par with Christianity and it's beginnings, and similarities found between them is just...wrong.