I have an issue.. It's when people say osas is justifying sin. I have not come across anyone in real life or on this site who believes osas and uses it to justify sin. Why do people continually say this? No right minded Christian will justify sin, it is against our nature (through the work Jesus has done in our hearts) to do so.
I don't use the phrase "once saved always saved" because it is associated sometimes with antinomians, who would hold this view.
In the USA there are a large number of individuals associated with some Independent Fundamentalist Baptist, Southern Baptists, Free Grace Movement, and Grace Evangelical Society (Robert Wilkin) organizations which do not believe in bibilcal repentance, and promote "easy believism" and "no Lordship salvation".
In other words, they have a diminished view of repentance as mere intellectual assent with no resulting spiritual fruit, and claim that a person can accept Jesus as Savior but not Lord.
This no-lordship view was a big battle in the dispensational camp, as one group focused on Lordship Salvation (led by John MacArthur) and another group focused on no-Lordship Salvation (led by Zane Hodges and Robert Wilkin). There are many videos on Youtube by Zane Hodge and Robert Wilkin which twist Scripture to support their false teachings.
Salvation is best viewed as union with Christ, and all of these claims regarding no Lordship salvation simply go away once Scripture is viewed in the light of union with Christ. The believer is united with Christ, and this union justifies him because he is one legally with Christ, therefore all of Christ's assets are shared with the believer, including his righteousness. Additionally, he is one vitally with Christ, and as a result he is spiritually joined with Christ, and is spiritually transformed over his lifetime. This transformation produces fruit of obedience and love through the union with Christ mediated through the Holy Spirit.
No one who has been joined to Jesus should have any reason to doubt his salvation and his eventual glorification. Read Romans 6:1-14.
I believe the major problem with the OSAS crowd is that they are a half-baked cake which does not consider union with Christ and the two aspects of it (legal and vital). They fixate on legal justification alone (the legal union) and not the vital, life-changing union. Their understanding has not developed to the point where they understand vital justification, although they understand legal justification (which is more than some works-oriented Christians know but is not the complete picture).
Nothing I have said denies the fact that the believer joined to Christ will inevitably experience the resurrection of the just on the last day, though. I don't believe that obedience justifies the person, and not a single person joined to Christ is lost. However, I am pretty sure that many are counting on a false faith for their salvation.
I just don't like using the phrase "once saved always saved" as it is associated with no-Lordship salvation people. I prefer "perseverance of the saints" or "preservation of the Holy Spirit" or even eternal security, although I think this phrase is also associated with no-Lordship salvation people too.