Where to start, Erdogan is very conservative and has a strong religious following. There have been countless demonstrations against him by the more progressive urban population, but if last week's local elections are anything to go by he'll be returned next year.
Yes, he is opposed to the Syrian regime, but like many conservatives is quite illiberal, as his banning of Twitter and Youtube testify. He's also quite paranoid which is probably quite understandable when you bear in mind the Turkish General's history of coups to protect Turkey's secular identity.
There's also Turkey's long struggle with trying to gain membership of the EU. In recent years Turkey has bent over backwards trying to accommodate EU demands, but Erdogan seems to have given up trying. Despite what the EU says there's an inbuilt hostility to allowing such a predominantly Moslem country's citizens the right to free movement across Europe. Some of that sentiment may be fuelled by racism, especially in the East European counties with memories of the Ottoman Empire. When I was in Crete the tour guides routinely referred to the Turks as barbarians.
From what I understand, his banning of Twitter and Youtube has very little to do with Syria, and is more about stopping the Turkish opposition making claims about corruption in Erdogan's inner circle.