Well its funny how you call any of it "protecting themselves". You see there is defense and there is having an army, performing raids, and generally speaking : Not against war in practice and speech.
So lets just say that, yeah, muhammed wasn't peaceful in practice.
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Ok lets go into having mutiple wives.
First off, researching here you find out some interesting things............
1. With muhammeds first wife(Khadija the merchant), he had 6 kids. 2 Sons and 4 daughters.
2. He did consumate the marriage with aisha.
3. God "forbade anyone to marry muhammads wives" in the Quran:
"Nor is it right for you that ye should annoy Allah's Messenger, or that ye should marry his widows after him at any time"
4. This too easy.
Lets start with 3 here.
Argument 1: Remarrying.
Its funny to me how "god forbid" anyone marry muhammad's wives but he could marry others. Kinda odd how this works. He married other widows, yet people aren't allowed to marry his. Odd even more how the quran forbid this. So god is ok with him doing the act, but no one else can?
Argument 2: Many wives
It seems odd how Muhammad who was sooo generous with charity and such. But he had to marry "certain" people in order to provide. In the tribe he was suggested to marry such people by the leader of the tribe. Aisha was at a young age, not consumated till later, but still. Then you have many widows, a slave, and other such things.
-Again, no one other than muhammed can marry this many by the religious laws, but muhammed can.
Both arguments are basically the same: The quran doesn't allow such things, but sure, muhammed can.
P.S.
I can debate on modern morals all i want and i would be right too. But you'll just dismiss it to "at the time it was ok" like a dumbass. So i tried to present you with a debate that contradicted the quran itself and therefore islam.