Why is intelligent design not a fact

In order for something to be a theory you need a lot of proof to support the claim. There is just not any proof that something designed life. It's not like science is trying to ignore this option (although I suspect some scientists do) we just can't find any evidence for intelligent design.

We have a theory for how life evolved, but as far as I know nothing really explains how it was possible for life to come into existence in the first place. Some people try to fill this gap with the idea of intelligent design and I guess there's nothing wrong with this, but it's far from being a scientific theory and it is extremely arrogant to call it a fact.

Just making the assertion that biological organisms are "designs" does not make it so. You must present evidence that organisms were designed, in order for them to be designs. Since you have not done that we will continue to consider them organisms.

An organism is not a design, just like a house is not a blueprint.

Hmmm. Decisions, decisions. Should I report you for ranting, or should I take your question seriously. Well, I'll do the difficult thing. I will pretend that you are actually uninformed and are asking a sincere question, no matter how difficult that is to believe.
Design, noun. A plan or scheme conceived in the mind. (The New Shorter Oxford English DIctionary)
Next time you need help with your vocabulary, please consult a dictionary first.
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Oh, sorry. Maybe I need to spell it out for you? You MUST have a designer using the above definition.
Let me know if I need to use smaller words.

Biological organism are complex designs that were formed over millions of years of trial and error, but they were not designed by another organism, like God. Intelligent design is the theory that all life was created by a supreme being, which most scientist reject!

There is definitely some intelligence in intelligent design.

Because our retinas are backwards. No intelligent designer would have made them that way.