If there was a single event marking the end of Ataturk’s political culture and replacement with sharia, this would probably be it as History tends to record it when these sorts of things happen to the famous.
New York Times:
ISTANBUL — A court here handed down a suspended 10-month jail term on Monday for Fazil Say, an internationally acclaimed Turkish pianist and composer convicted of insulting Islam and offending Muslims in postings on Twitter.
Mr. Say, 42, who has performed with major orchestras around the world in places including New York, Berlin and Tokyo, said during earlier hearings that the accusations against him went “against universal human rights and laws.” The sentence was suspended for five years, meaning that the pianist will not be sent to prison unless he is convicted of re-offending within that period.
In recent years, many intellectuals, writers and artists have been prosecuted for statements about Islam and Turkish identity, both of which the pro-Islamic government seeks to shield from criticism.
You are right, this marks the end of secularism in Turkey.