why do people that don't believe in god have so much to say against him [Spirituality & Religion]

I've always wondered why these individuals are so threatened and so angry at someone they say doesn't exist and never has existed.

You're kidding, right ?
Well, if you know your history you'll know that certain believers have been telling the rest of us, for hundreds of years, how we are the select few going to a place you call Hell !
Naturally, if history shows you how non-believers have been burned at the stake and other delights, in THIS life,isn't it reasonable to assume folk would have a great deal to say against there being a God ?

I think atheists need to feel they are in control and any mention of a god is a threat to them. That's why they get so angry and offensive quite often

What gets me most angry about the god-issue is that the religious say he/she/it/they allow horrible,senseless acts and events to occur, as 'part of gods plan'. Totally unacceptable. Any god that would include massive amounts of senseless horror is unacceptable as a god, and should be overthrown.

I’ve [b]never[/b] had an atheist stop me on the street to proselytize, [b]nor[/b] have I had one knock at my door saying, “don’t believe”. 🤔

Same reason people that believe in him think they can look down on people. Or manipulate, create, and ignore laws because of faith. And I'm not just talking about Christianity.

i think a part of them might feel threatened. what if they are wrong and it's al true. that is pretty scary and fear always breeds contempt.

Like the rest of us, they want to be validated :)

I think some of them just want a fight. I think some of them just want to correct what they perceive to be an irrational belief.
As for myself, most of the time i only talk about god with respect to people who deny the theory of evolution in favour of the book of genesis.

To explain the reason(s) for their disbelief!

They need to justify their ignorance somehow.