I thought they're called "teddy" bears because there once was an US president who's first name was something like Ted. And when he wanted to shot a bear, he just couldn't do it. And ever since they're called teddy bears.
Don't shoot me if this answer is wrong, I have no idea where I heard it but it's somewhere in my mind haha! xD
If 당신 ask me, they aren't aggressive at all. They hunt, and they defend. I'm not a bear-expert, so I'm just saying what I think about the subject... xD