The Turkish governtment may not recogninze the freedom of expression, but it is still an important human right. Praising the coup was not an act of terrorism, it was simply expressing political beliefs. The arrest of these people was a clear and obvious example of violating thier freedoms and rights.
The coup attempt in Turkey kept the world on the edge of its seat. The coup ultimately failed though. Now the President of Turkey is cracking down and showing exactly why the coup was attempted in the first place, he's a tyrant. By silencing those that disagree with him Erdogan is silencing different viewpoints and violating the freedom of expression.
Yes, it appears that in this case, freedom of expression is being violated. I don't agree with supporting the coup attempt, but I don't think that people who do support it should be imprisoned just for saying so. I think there are far more important criminal matters to focus on instead. People should not be afraid to express what they feel.
Yes, I believe they are violating freedom of expression. Removing freedom of speech does very little to prevent things like coups and civil wars; instead, it drive rebels underground, where the problem brews to a very dangerous boiling point. This creates an illusion that things are okay until they finally explode, similar to what's happening right now in several other countries. Allowing people to speak freely is an important part of freedom.