> the world still need to see some solid evidence
I agree completely with your sentiment regarding conviction without proof, but want to comment on this thought one part for a second, in isolation from the rest of the discussion. First of all, that the world doesn't see evidence on gulen's shady dealings or extreme islamist tendencies at all is a measure of the world's own ignorance. I don't mean this in an accusatory way - it's not your fault.
Outside observers, especially those who do not understand Turkish, are excluded from huge swathes of news, discussion, court cases and information. What you're getting is the gist. It's second hand information at best, and the foreign media often gets it wrong, misses historic context, or glosses over the nuances.
Just like all the people here (and in western news organizations) who didn't know Gulen existed up until very recently - an deficiency in knowledge so huge that it should scare you away (and perhaps disqualify you) from holding a strong opinion on Turkish politics immediately.
So when outsiders ask for "evidence" - really they're asking for a New York Times / Economist / Wall Street Journal / Foreign Policy op-ed. Because that's considered a respectable news organization, but Turkish sources aren't considered respectable, never mind that they probably share most of their sources on Turkish news.
So, demands for "solid evidence" in this sense are a measure of privilege that's so monumental that people don't even realize they're subject to it.
So when I try to make an argument with someone who isn't from Turkey, the best I can do is point to sources like these, which all have surface-level milquetoast reports on gulen, painting him a "reclusive cleric", an islamic scholar and "supporter of interfaith dialogue" - all true to some degree, but definitely not the whole story.
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As a more concrete example, let's look at the progression of Gulen profiles in the nyt over the years:
2000 http://www.nytimes.com/2000/08/25/world/turkey-assails-a-rev...
2008 http://www.nytimes.com/2008/05/04/world/asia/04islam.html
2010 http://www.nytimes.com/2010/06/12/us/12iht-gulen.html
2012 http://www.nytimes.com/2012/04/25/world/middleeast/turkey-fe...
2016 http://www.nytimes.com/2016/07/17/us/fethullah-gulen-turkey-...
2016 http://www.nytimes.com/2016/07/20/world/europe/fethullah-gul...
It's amazing to see how the language and the detail in the account of his activities change across the years. The 2000 article gets the part about the prosecution, but misses the point on Gulen completely. Nor a single bad thing about him. Anyway, recently, they gave the soapbox to gulen himself twice:
http://www.nytimes.com/2015/02/04/opinion/fethullah-gulen-tu...
http://www.nytimes.com/2016/07/26/opinion/fethullah-gulen-i-...
Luckily, they also gave a smaller soapbox to Mustafa Akyol, a Turkish journalist, who presents many great counterarguments:
http://www.nytimes.com/2016/07/22/opinion/who-was-behind-the...
Again, I don't think this is some conspiracy, but just ignorance. The 2000 article was ignorant of basic, common knowledge in Turkish politics. The more recent ones are less ignorant.
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Of course this is changing: for example here's a 2014 article from the Carnegie Endowment, which points fingers to shady activities but doesn't make accusations about islamism:
http://carnegieendowment.org/2014/02/04/g-len-movement-and-t...
Turkish sources are also starting to publish english language news - here's an analysis of the Gulen movement through wikileaks cables:
http://www.dailysabah.com/politics/2014/04/04/cia-fbi-divide...
Here are some of the actual cables - I hope these are considered reliable to draw your own conclusions from:
https://www.wikileaks.org/plusd/cables/05ISTANBUL1336_a.html
https://wikileaks.org/plusd/cables/09ASHGABAT491_a.html
See Centicosm's comment here for another well researched article:
http://www.meforum.org/2045/fethullah-gulens-grand-ambition
It also comes from the Middle East Forum which is a conservative think tank, so take that as you will. But this is what I mean - they have a huge incentive to badmouth islam, so they actually bother to engage in research. Impressively, most of the sources on the bottom are Turkish language sources.
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Anyway, my point isn't about gulen, but the attitude and the cultural notion that facts exist when they exist in the western media, and anything else is unreliable conspiracy theories and bunk. And this coming from people who barely knew Gulen - a central figure in Turkish politics - a few months ago.
Yes, things do suck in Turkey, and are nonfunctional in many ways. Many things are wrong, many sources are unreliable and corrupt, but we're not completely stupid either, and the sneering sense of superiority I so often encounter is counterproductive, surprising and tiring.