Overzealous corrupt religious fanatics who base their bigotry and prejudices off their holy text, who have their heads stuck in the sand, and claim that people who do things their book says no about are evil sinners, while not looking at all the sins they themselves commit.
This question is unanswerable on a global scale..
It's too relative..
There is no objective truth within the scope of human perception.. Whatever anyone says.. It's highly subjective and open to valid scrutiny.
Because whatever example you give, you give with rationalization.. But whatever you find irrational, the other finds completely rational. and can rationalize just like you can.
Rationalization in itself is irrational, and thus.. A paradox.
You do not build true knowledge through the removal of data but rather by compounding data.. Not by limiting possibility, but by expanding on it.
unreasonably irrational.... There probably isn't such a thing.
I think there is a reason for everything. things only seem irrational. the fundamentalist fanatics or whatever are sticking to their crazy beliefs as it strengthens their own community. or it allows them to be part of this group. being rational can be very a lonely thing. people who buy overprized stuff are choosing time (not looking for the same thing for less) over money. and it goes on and on.
I gota agree with @pigeon on that. I can't think of a better example then overzealous religious people. I once had a guy tell me I was going to go to hell because I was wearing all black. The dude didn't even know me!
People with a negatively corrupt ego and a high sense of self that causes them to want to spread that corruption and cause people problems in order for that individual to gain what he/she believes he/she wants when in reality that behavior is based off of materialism, putting value into items that, without the involvement of the human ego, would be without such value.
Examples: Warfare, genocide, dictatorships, powerful governments, money, corrupt corporations, brainwashing, false religions, censorship... basically anything in the world seen as negative that we choose to do nothing about.
In my honest opinion, I believe that these things are here to teach us so we can better ourselves, yet are completely unnecessary as all we really have to do is look within ourselves to find the answers to things and to reach the positive goals we all want to accomplish. In such, even though it serves a purpose, these things that are all the creation of the negative human ego is unreasonably irrational. I mean who truly, from the soul, wants to suffer or cause suffering to a fellow human?
Like someone else said, it implies that you can be reasonably irrational which doesn't make any sense. Unreasonable and irrational are basically the same thing so it's a bit redundant to say.
-An example for me is - someone who claims to be a very rational person yet doesn't take emotions into account and writes them off as irrational like they hold no importance what so ever even though they are very much apart of them and others. Someone who is unaware of how much they are pulled by their own emotions but says they are being completely objective.
-People who choose not to think about why they do things.