Why do I say that Islam is an evil religion?

[Eclectic]

The word "evil" is meaningless outside of religious language. Since you purport to be an agnostic, you can't use this word without contradicting yourself. 

And there you go, your entire worldview has just been toppled.

 No religion has any authority over words! To actually state that for an Agnostic to make use of the word "evil" is a contradiction of themselves is just about one of the most ridiculous statements I have heard in quite a while.

And there you go; your entire worldview is meaningless in itself.

Iranians use the words Satan and Evil as adjectives.
It is not a proper name or a common name.
For example, let's say:
You are very Hitler.
And we mean you are very racist.
For example, let's say that Israel is very Hitler.
We mean that like Hitler who brought disaster to the Jews, Israel is bringing disaster to the Palestinians.
But you come to tell us that Hitler and Israel are enemies, so Israel cannot be Hitler.