what exists and what doesn't exist depends entirely on whether it can be observed to exist
a scientist may claim that something doesn't exist because he is unable to observe any proof of that something's existence
but to the person who may have observed that same something, it DOES exist, regardless of whether he has any proof to offer
Let's think of a generic scientists, and call him... hm... Peter. Peter observes. He gathers information from those observations. And he tries to explain those observations with a theory that seems logical, and that is based on those observations and on knowledge Peter already had. Next, Peter gathers more information to try to prove his theory, and presents it to the rest of the scientific community, so that they can check that theory out. Maybe they find information that proves that the theory is true. Maybe they find information that proves that the theory is wrong. In the latter case, Peter will have to come up with another theory.
That's what Peter does. Peter doesn't claim randomly that something somebody else claims is wrong for no reason whatsoever. And of course you are right, reality takes shape in our heads. However, if a person claims that something exists. And that person has no evidence, and no logical theory, and can't reliably make others experience the same, and if what that person says doesn't seem to make sense to Peter based on what he already knows: why should Peter assume that what that person says is true?
If someone tells me "I saw a demon".
And if I reply "I don't believe that demons exist".
Then both of us have an opinion based on the experience we made and what seems to make most sense to us.
Why would that make me evil, just because I don't randomly believe everything?
Especially considering that I give each and everyone the chance to convince me that my current opinion is wrong. If you say "I think that we have microscopic invisible unicorns grazing on our heads", then I also say "that doesn't make any sense to me, but feel free to convince me otherwise".
In many ways I stick to my intuition and to my emotions when it's about deciding stuff. In many other ways, I stick to logic. What's wrong with that?
Why is saying "I think that my blanket is filled with anti-matter and pixie dust" good, and saying "I don't think so" bad? Why are people who doubt things that can't be proven, that make no sense, that are logically flawed, automatically "evil" according to some people?
Is it because so many people long for supernatural things? For glittering vampires that might give them immortality? For a life after death? Maybe especially people who have some social anxiety problem often flee from the reality as it is, and change it intp their mind in something more magical, something more friendly than the world they know? Maybe that's why some people are so sensitive when someone says "that makes no sense", because they fear that their protection from the world as science tells us it is might fall apart if they lose their faith in the supernatural? That they either get aggressive or flee when someone says something that might destabilize their magical forcefield to keep out reality and give their life a higher meaning?
In that case: sorry. I try to be open minded in so far as I consider anything that seems remotely logical to me to be possibly true. But the same I also consider stuff that makes no sense to me to be incorrect. That's the way I am.