Constructive engagement has been tried with Turkey and failed. Turkey has reaped the benefits and failed to deliver anything in return. For many the brutal attack on peace campaigners who were part of an ill-fated mission to instigate peace talks between Turks and Kurds was the last straw. As a matter of sanity the West has to cut arms sales to Turkey. These weapons are used for internal repression and external aggression.
Pressure has to be applied on politicians to severe all links with Turkey.
Whether or not the West agrees to isolate Turkey, the consumer can. Turkey requires hard currency to purchase its weapons. Consumers should boycott holidays in Turkey, boycott produce from Turkey. If you see produce from Turkey, explain to the manager or shopkeeper why you find it offensive and that it be withdrawn from the shelves. Tell travel agents why they should withdraw from Turkey and why it will not be on your holiday itinerary.