All that believe are or have been Justified !
Even though false religionists dont believe it, wont accept it, nevertheless it must be preached, but only those who have been Justified, by the Merits of Christ's blood shed for them, do and can believe ! The reason why the masses of people dont believe and will not believe on Christ, its simply this ,They cannot because they were never of His Sheep Jn 10:26
26 But ye believe not, because ye are not of my sheep, as I said unto you.
So they cannot believe Jn 12:37-39
37 But though he had done so many miracles before them, yet they believed not
38 That the saying of Esaias the prophet might be fulfilled, which he spake, Lord, who hath believed our report? and to whom hath the arm of the Lord been revealed?
39 Therefore they could not believe, because that Esaias said again,
God gives only them Christ actually died for the ability to believe on Him, for His sake Phil 1:29, those only for whom He suffered and died, and by that, did satisfy all His Law and Justice FOR THEM ! All for whom He died He made them declared Righteous Rom 5:18-19
18 Therefore as by the offence of one judgment came upon all men to condemnation; even so by the righteousness of one the free gift came upon all men unto justification of life.
19 For as by one man's disobedience many were made sinners, so by the obedience of one shall many be made righteous.
And to them this Righteousness and Justification of Life is revealed to God given Faith Rom 1:16-17
16 For I am not ashamed of the gospel of Christ: for it is the power of God unto salvation to every one that believeth; to the Jew first, and also to the Greek.
17 For therein is the righteousness of God revealed from faith to faith: as it is written, The just shall live by faith.
Understand, The Gospel makes known to them that Christ died for, the results of His death, Righteousness to them and or Justification of Life, For they had been freely Justified by His Grace through the Redemption [its efficacious value] that is ni Christ Jesus Rom 3:24
24 Being justified freely by his grace through the redemption that is in Christ Jesus: