If his supporters would come out,it would be all out war(Erdogan knows that),voting for Erdogan and beeing his supporter are two different things.
Most of the people voted for his economic achievements,they tought he does well.
People didnt know then(at least most of them didnt) what he is trying to do(turning the country in a new caliphate).
As you can see there are NO political parties on the streets,just people from kemalist,communist,rightestsetc to even islamists).
All sides united against Erdogan,people just letting him know;Dont go to far!
Is it a protest because of your existing GOV is trying to impose more Conservative religious thoughts on a secular Turkey Society?