Laurie the attacks on the beach you mentioned in your post weren't in Turkey...
Seeing as the Italian police have warned today about - apparently - concrete threats on European beach resorts (not to mention the possibility of CBRN attacks on the UK) this summer, it's really not much different if you're after a beach holiday, in all honesty. Where do you stop drawing the line, at the end of the day? People go the Maldives and Mauritius, where there are periods of severe political unrest, as well as Islamist instability in some cases, but don't care (or, more likely, have no idea, even before they go) as they are tucked up in their all inclusive resorts. Thailand has an Islamism problem (as I assume that's really what the OP is about), as does North Africa, East Africa, West Africa, the Philippines, parts of China, parts of India - etc etc etc
Speaking personally, I think it's only a matter of time before something happens in a Turkish coastal resort: but then, I strongly suspect it's only a matter of time before the next attack in mainland Europe, and sadly, it's definitely only a matter of time before the next attack in the UK. Remember, a terrorist only has to be lucky once- the security services have to be lucky all the time. The only advantage of Turkey, in that respect, is the minimal respect for human rights that Erdogan and his cronies have, so you can be sure they smack down hard on anyone they don't trust - so at least you'll be safe from the PKK 
It's your holiday - you've got to do what you feel comfortable with: but statistically speaking, you're still safer now than at any other time in human history - though I appreciate that when you become one of the statistics, that's not much comfort.