An apostate is someone who renounces his former beliefs and actually sometimes acts against that belief or the leader or leaders of that belief. What makes the individual an apostate is this act of active opposition to his former beliefs and the remaining adherents of that belief.
It is often better to keep quiet if one’s convictions about a particular spiritual belief have changed. The burden of guilt is too great if one goes public in one’s renunciation of one’s former beliefs especially in a negative way, thinking that one is thereby protecting others from this belief, or in other words, thinking that one is thereby doing the public a great service this way.
One is thereby exposing oneself to evil currents which will ensure that one is pushed further downwards to dark regions. A noble person will never act in this way. He will always assume that it was all his fault that he became involved in such a belief in the first place and will quietly walk away. This way, he will never burden himself with any guilt and will always be free.
This was the case with Judas when he turned against his Master and ultimately betrayed Him, thereby burdening himself with enormous guilt in the process.