MrPaul,
With respect, you are speaking to some here who know Greg Violi personally, and who have personal testimony of his ministry in both preaching and prayer.
Of course it is natural for demons to be disturbed by the presence of one who is filled with the HOLY Spirit. We read of this in Mark's third chapter (Mark 3:10, 11), in the presence of Jesus Christ the Son of God.
If we believe that Jesus Himself is in us by the Holy Spirit (see John 17), the same may happen - that as the minister (for instance, Greg Violi - but I know of others also) seeks the word of God for a troubled soul, he is directed to send an evil spirit away.
Afterwards, a believer may face difficulty in abiding in that liberty, because their mind may not yet be renewed; they may not understand how the spirit used to affect them. It is necessary for the person to be very open to the Lord for further correction and understanding, or, as Jesus warned, that spirit, and others, may trouble the person's life: Matthew 12:45, Luke 11:26.
Always where there are evil spirits, there is a failure on the part of the Christian to accept the effect of the cross in their life.
All Christians MUST understand that to be free from sin (have victory over sin, self and devils), they MUST receive the SPIRITUAL effects of the DEATH of Jesus Christ, IN THEIR OWN heart, and mind, and body. This is a personal transaction with God which will lead to observable changes in that person.
Pride is the main issue which prevents a person from accepting, or demonstrating, their own need for internal change.
Flesh is very strong, but Jesus Christ is stronger - if we will receive Him INTO our WHOLE lives.