If “a practicing sinner” means a person who is openly approving of sin and is engaged in it, can this person be saved? Yes and no. Yes because any sinner has the potential of becoming saved. On the other hand, if the person is professing to be a Christian yet is unrepentantly practicing sin then it would appear that he would not be saved. 1 John 2:4 says, “The one who says, ‘I have come to know Him,’ and does not keep His commandments, is a liar, and the truth is not in him.” So, a sinner can be saved, but once saved, the Spirit of God will move that person to repent of their sin. If a person continues to practice unrepentantly, promoting it, etc., then that person would not be demonstrating evidence of regeneration.
But then again, a person could become saved, still fall into sin, be convicted by the Spirit of the sin, and all the while seek to break free from it. So technically, in this last sense, he could be saved and be a sinner not as a life style, but as in struggling against his sin which sometimes can get the best of him. It would be like a drug addict becoming a Christian and still being hooked on drugs. He would struggle against it and still have the desire to participate in it.
I would say that a person who has professed Christ and is struggling against sin is demonstrating evidence of regeneration. Remember, many people who become Christians still struggle with many of their old sins. Even Paul struggled, “For the good that I wish, I do not do; but I practice the very evil that I do not wish,” (Rom. 7:19). We are not perfect and we must remember to be gracious to others, especially when they are stuck in an old sin, want to repent of it, and are trying to have victory over it. This is when grace is needed, not law. But, of course, we are never to encourage or excuse a person’s sin. We must pray for them to attain full victory.
Now, some Christians will state that once you become saved, you should automatically have victory over all your sins. This is an unfortunate burden they place on many Christians because “perfection” becomes the standard for measuring whether or not they are Christians. This can cause people to doubt their salvation. While it is true that we have victory in many areas when we become saved, it is also true that we still struggle with many of our old sins. Of course, it is never okay for us to go ahead and sin (Rom. 6:1-2). We must always struggle for holiness. But the fact is, like Paul, we sometimes do the things we don’t want to do and don’t do what we should. It is our struggle against sin that demonstrates that we are regenerate since we are seeking to be holy as God is holy (1 Pet. 1:16).
Finally, no dead people struggle for life. Only those who are alive struggle. Likewise, the dead in sin, the unregenerate do not struggle against their sins. Christians do.