They are some of the most ingenious people. They will make a weapon out of anything they can get their hands on, no matter if we supply the materials or not. And it is really simple, if you understand the mechanics of a gun, to switch it from semi automatic to automatic. We could destroy all weapons, knives, bows, guns, and they would still find a way to kill.
That's making an awful lot of assumptions.
"They are some of the most ingenious people"
Really? What's your basis for saying that? I imagine that may well be true for a few, but the vast majority are ~not~ some of the most ingenious people. XD
"They will make a weapon out of anything they can get their hands on, no matter if we supply the materials or not."
Assuming they have the knowledge and skills to, it would still in most cases be nowhere near as effective as a manufactured firearm. In fact, in first world countries I don't think I've ever heard of killing sprees with improvised weapons because the perpetrator couldn't get a hold of any real guns.
"And it is really simple, if you understand the mechanics of a gun, to switch it from semi automatic to automatic."
~If~ you understand the mechanics of a gun, which I'm guessing most don't. Besides which, if Semi Automatic guns were also banned or more restricted, that point would make little difference.
"We could destroy all weapons, knives, bows, guns, and they would still find a way to kill."
No, they wouldn't. I imagine only a portion would still try, and a much smaller portion would succeed.
You're painting them like some Hollywood aliens, where they're all identical and use their superior intellect to ensure the destruction of humanity at all costs. It's ridiculous XD