In these verses, Paul appears to levy absolute, generalizing accusations upon all Jews. Among the reasons that his words cause concern are: (1) these statements are inconsistent with others Paul makes concerning his Jewish contemporaries, and (2) these words have fueled anti-Jewish behavior and rhetoric throughout the history of the church.
Before assuming the worst about these verses, one should note that Paul could be saying several different things. His words can perhaps be taken to support one of the following:
Paul's statements here appear to go beyond simple, overenthusiastic polemic. They read as an overstatement, one that too many subsequent readers unfortunately have applied with harmful consequences. Whatever Paul's reasons for these words, interpreters do well to remember that the wider context does not suggest that this is Paul's definitive treatise about the state of all Jews before God. He was a Jew himself. Paul's main point is to describe the opposition that the Thessalonian believers are enduring. He does this by comparing it to fervent opposition that believers have faced elsewhere.
14For you, brothers and sisters,* became imitators of the churches of God in Christ Jesus that are in Judea, for you suffered the same things from your own compatriots as they did from the Jews, 15who killed both the Lord Jesus and the prophets,* and drove us out; they displease God and oppose everyone 16by hindering us from speaking to the Gentiles so that they may be saved. Thus they have constantly been filling up the measure of their sins; but Gods wrath has overtaken them at last.*
New Revised Standard Version Bible: Anglicized Edition, copyright © 1989, 1995 National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved worldwide. http://nrsvbibles.org