Why is it acceptable only in Islam...?

The term "Islamist" was created to distinguish in political speech between

Muslims

and those people and organisations who use Islam as a tool for exclusivist political power (essentialy Nationalist entities using Islam as their justification).

Likewise, "Jihadist" was created to distinguish Muslims from those people and organisations who essentialy have declared war against the non-Muslim world and justify this as Jihad.

It is a way to at the same time respect normative religious Islam

and be able to discuss and criticise the dangerous organisations who use Islam as their justification for being.

Quranist is not acceptable, you make things up.

Evolutionist is more accurate that Darwinist,

You have the audacity to assume that English is the sole language in this world

Some may call themselves anything they wish but that does not make it True

Suffix-ist

.Added to words to form nouns denoting:

1.One who follows a principle or system of belief.

Marxist, deist

Note, these are related to -ism, e.g. Marxism, deism

2.A member of a profession or one interested in something.

botanist

psychiatrist, one who studies psychiatry

3.A person who uses something.

violinist, one who plays a violin

4.A person who holds biased views.

sexist, racist

They get called "Islamists" because it offends Muslims when the news refers to "Muslim" extremists.

What? Do they not exist or something?

EDIT - also there's no such thing as a "Darwinist".

...

A better question would be why are you Islamics so sensitive. You people take offense at every turn!

If you truly believe your silly religion you'd be much less sensitive.

Taoist/Atheist (realist)

"Quranist" has a nice tune to speak unlike the other examples. it reminds me a planet name

Jesuit?

never heard of those words but then again, i dont watch much fox news.

Islam is being of the one true religion of peace. You are being of such with this or we are being of chopping off your heads!