But why were there protests in the first place? Because he wasn't being too nice to other groups in the country. So the best thing is to remove him and bring in democracy for all - a lot easier said than done, though.
JK, Syria has a large majority of Sunni Muslims, and President Assad leads the Ba'ath Party - a predominantly Sunni party. The original demonstrations were from very small the Shia minority. Whilst ISIS are nominally a Sunni organisation they are extremist in their views and regard Assad as a 'traitor' to the Sunni cause because of his willingness to protect the other minorities including Arabs, Greeks, Armenians, Assyrians, Kurds, Circassians, Mandeans and Turks. Religious groups include Sunnis, Christians, Alawites (nominally Shia), Druze, Mandeans and Yazidis. (these two lists are from the wikipedia article on Syria).