This in itself says nothing about the moral character of epilepsy sufferers. Demons attack us in different realms, but Jesus in us is more than enough to overcome them, if we remain in Him. And as they were going out, behold, a dumb man, demon-possessed, was brought to Him. All it means is that the man had a demon which affected him. The word 'possessed' is misleading because it leads us to think that Scriptures like this are not generally applicable to the cases we find in life, when in fact, they are.
Demons are still active in defiling mankind today.
Their attacks are directed not only against the spirit and soul of mankind, but also against his body. Armed with this knowledge, we have powerful motives to understand God's opposition to sickness and disease and to have faith that He really does want to heal. By entering into the conflict with this conviction, we enter into conflict with demons, which we must overcome by means of the spiritual weapons which God gave us. God is a good father. No good father ever wilfully made his child sick.