I dont think "terrorists" belong to any religion.
I agree. It's like saying violence is linked to one religion.
I dont think "terrorists" belong to humankind at all.
And I very much disagree with this.
I won't get into a large controversial discussion of it here, but this is just the sort of dehumanization that is wrong and increase the problem rather than solves it.
Some terrorist behavior can be 'insane', evil, brutal, and inhumanE, as opposed to inhuman.
But it's definitely human. To say otherwise is to oppose the understanding - a word the right often confuses with 'agreeing' -that is important.
Also, the ability to understand AND IF APPROPRIATE AGREE with grievances is helpful, something else the right often doesn't understand.
Some terrorism has no case - it's hate, ignorance, superstition, cult-like indoctrination that justifies the harming of innocent people, period. But oh wait, the two million Vietnames killed, by bullet, agent orange, napalm, torture and more for our own 'excuses', that's better how again? And have we come to recognize the wrong? Most haven't.
But other terrorism - and you can still attack it much of the time as wrong - has roots in oppression. When a government is terrible to its people - kidnapping, torturing and murder any who oppose the repression and even some who don't just to keep the people scared - people might fight back with terrorism, in an attempt to motivate more of the public to take up the battle, creating instability, making the government look vunerable to encourage opposition to it.
The issue is more complicated - but the basic point here I'm making is that 'inhuman' is a word that has no place discussing human behavior, however bad.
It creates walls against dealing with the problem. "Oh, they aren't human, and that's the end of the story." No, it's not and sometimes, it prevents any justice as well.
Sometimes, violent supression of terrorism is the best choice; other times, violent supression of terrorism is protecting injustice; but it's human behavior.
Even if it's setting off a nuke in a city that killed masses of innocents, even if it's blowing up a school bus of children, even if it's bombing a village from a B-52, it's human.
Al-Qaeda/Osama bin Laden was responsible. If I know my facts correctly, he/thr group was equipped by American funds and know-how than by Islam to plan and implement the dastardly act.
There's something to that, but I don't know most came from the US; I thought I saw they have their backers among the radicals in Saudi Arabia, for example.
I've recommended a book on the US (and English) role in the sponsoring of terrorist groups in the Middle east, to create forces against the nationalists and take power, called 'Devil's Game'. You might benefit from it as well, helping clarify some of the history you may not have seen of how these groups got started. It should be history taught in our schools that Americans learn, but it's far from that, as the false myths we had nothing to do with it are held by most.