“Comparing Paul’s theological argument to Christians in Romans 1 with his evangelistic preaching to pagans recorded in Acts, there is a marked difference of tone, even though there is certainly no clash of fundamental conviction.”
“Romans, written to Christians, highlights the wrath of God. Acts, referring to speeches made to pagans, highlights God’s kindness, providence, and patience. Both, however, insist on God’s judgment.
-Romans portrays idolatry as fundamentally rebellion and suppression of the truth. Acts portrays it as ignorance.
-Romans portrays the wickedness that idolatry spawns. Acts portrays idolatry as ‘worthless.’
-Romans points out how perverted the idolater’s thinking has to be. Acts points out how absurd it is when you stop and think about it.
-Paul could excoriate idolatry as ‘a lie’ before Christian readers, but did not blaspheme Artemis before her pagan worshipers.”
“So there is a difference in tone and tactic in Paul’s confrontation with idolatry, depending on the context of his argument. However, we should be clear that in both cases, he is building all he has to say on very solid scriptural foundations, for every one of the points mentioned above, even though they have differing and balancing emphases, can be related to the Old Testament’s rhetoric against idolatry. It is particularly noteworthy that although Paul nowhere quotes Old Testament texts in his evangelistic preaching among Gentiles (as he so profusely does when speaking among Jews in synagogues), the content of his message is thoroughly grounded in and plainly proclaims the monotheistic creational faith of Israel.”
This is (obviously) a summary of a larger argument, but it is a helpful one. For more on this topic, be sure to get Christopher Wright, The Mission of God. The above quote is found on page 182 of this book.