A lot of non-believers also survive marine corps boot camp...does that make them true real Christians, too?
Dedicating your life to Jesus Christ the Lord and Saviour is what makes a person a Christian...not what schools or training we have completed.
A cross is NOT a graven image. Nor did JESUS instruct anyone to worship a cross. And JESUS was NOT talking about salvation, either. It is living a Christian life.
Taking up a cross is equivalent to assuming a self-sacrificing life-style and putting JESUS first. Think about the supreme sacrifice...