There's no democracy if people are dying of terrorism. The first principle of freedom is that people have the freedom to know that they can go about their lives without dying. It's important that these people can feel safe in their own country. The president is correct to want to keep his people safe.
It is too easy to fear the stranger. Yes, beefing up security is a must. Making a police state is one step away from a dictatorship, and it isn't that big of a step. Pay attention to North Korea, they do not fear terrorists, but who wants to live there?
No, fighting terrorism does not outweigh democracy. If you give up your rights to defend yourself from terror the terrorists have already defeated you. Democracy is the opposite of rule by terror and therefore democracy is the only way to prevent the latter. Furthermore, the idea that safety and democracy are mutually exclusive is an idea put forth by those who benefit by taking away your freedoms. Anyone who says such a thing, such as the Turkish president, should be immediately relieved of their position.
Turkey has never had democracy, so they cannot try to preserve it. The modern country of Turkey was built upon the genocide of Greek and Armenian people. They are historically guilty of terrorism themselves, and they still silence people who speak up about these atrocities within their country. So they are in no position to state they will be fighting terror.