Thank you for showing us how a verse can be taken out of context and forced to mean something the author is not meaning.
Here is the text. Note that it has nothing to do with salvation by virtue of free will. It only shows that in some areas God allows us choice as it fits within the full will of God.
Philemon 1:10-16 I appeal to you for my child, Onesimus, whose father I became in my imprisonment. (Formerly he was useless to you, but now he is indeed useful to you and to me.) I am sending him back to you, sending my very heart. I would have been glad to keep him with me, in order that he might serve me on your behalf during my imprisonment for the gospel, but I preferred to do nothing without your consent in order that your goodness might not be by compulsion but of your own accord. For this perhaps is why he was parted from you for a while, that you might have him back forever, no longer as a bondservant but more than a bondservant, as a beloved brother—especially to me, but how much more to you, both in the flesh and in the Lord.
Notice that Philemon is the Master over Onesimus. Onesimus is bound to Philemon and Philemon has the God-given choice in this matter regarding what will happen to Onesimus. Yet Paul makes appeal as he considers that God has a much bigger purpose in redeeming Onesimus. Therefore, Paul places Onesimus on equal footing with Philemon and urges Philemon to recognize this as well.
On this earth, Philemon had the authority (capacity) to decide Onesimus fate, but Paul reminds Philemon that God has authority over all, so Philemon should therefore grant clemency to Onesimus for the sake of the gospel, which overrides earthly authority.
This interaction has, therefore, nothing to do with the capacity of men to choose their own salvaion by virtue of free will. Just look at Onesimus who is still bound in slavery. He has no capacity to be free of his bonds to Philemon simply because he wants to remain with Paul.