Burton Mack writes of 1 Thess. 2:14-16 in his Who Wrote the New Testament? (p. 113): "The person who made this change was interested in directing Paul's apocalyptic preachments against those who opposed the Christian mission and did so by inserting a small unit aimed specifically at the Jews who 'killed Jesus' and 'drove us out,' for which reason 'God's wrath has overtaken them at last.' Nothing in all of Paul's letters comes close to such a pronouncement (Pearson 1971). The idea seriously tarnishes the inclusive logic of the Christ myth, and it presupposes the logic of Mark's passion narrative which, as we shall see, runs counter to that of the Christ myth. And since, according to this addition, it was the Jews upon whom God's wrath had (already) fallen, the reference must surely be to the destruction of the temple in 70 C.E., an event that Paul did not live to see."
Udo Schnelle comments on the same passage (The History and Theology, p. 48):
I Thess. 2.14-16 has often been regarded as a post-Pauline interpolation. The following arguments have been based on the content: (1) the contradiction between Romans 9-11 and 1 Thess. 2.14-16. (2) The references to what has happened to Jews as a model for a Gentile Christian church. (3) There were no extensive persecutions of Christians by Jews in Palestine prior to the first Jewish war. (4) The use of the concept of imitation in 1 Thessalonians 2.14 is singular. (5) The aorist eftasen (has overtaken) refers to the destruction of Jerusalem.
Schnelle maintains that these arguments are insufficient (op. cit., p. 48):
(1) The tension between 1 Thessalonians 2.14-16 and Romans 9-11 goes back to Paul himself. It is a problem that needs to be explained, not a problem to be set aside by interpolation hypotheses. (2) Paul's ecclesiology presupposes a church of Jewish and Gentile Christians, so that Jewish Christians in Palestine can in fact serve as a model for Gentile Christians elsewhere. (3) Prior to 70 CE there were already conflicts between Jews and Christians in Palestine (cf. Luke 6.22). (4) The concept of imitation in 1 Thessalonians 2.14 is found already in 1 Thessalonians 1.6. (5) 1 Thessalonians 2.16c does not have the destruction of Jerusalem in view, but Paul sees in the hostile conduct of the Jews that the wrath of God has come to completion.
Raymond Brown mentions two additional reasons that the passage might be considered to be an interpolation. The first is that, "It constitutes a second Thanksgiving in the letter" (An Introduction, p. 463). The second is that, "The statement that the Jews 'are the enemies of the whole human race' resembles general Pagan polemic, scarcely characteristic of Paul." Yet Brown goes on to mention arguments in favor of authenticity (op. cit., p. 463):
(a) All mss. contain it; (b) Paul speaks hostilely of 'Jews' as persecutors in II Cor 11:24, and he is not incapable of polemic hyperbole; (c) In Rom (2:5; 3:5-6; 4:15; 11:25) Paul speaks of the wrath of God against Jews, so that the hope of their ultimate salvation does not prevent portrayal of divine disfavor.