The original post seems to imply that Paul chooses homosexual activity as something that both incurs and is evidence of God’s wrath in Romans 1 because he see it as a worse sin than other sins.

But the structure of Romans 1 seems to suggest he chooses that example because homosexual activitiy is a paradigm sin; a clear example of the rejection of the order of things instituted by God in creation.

Thus Romans 1 in no way implies either the worseness of homosexual activity or that slave ownership is OK. In fact Romans 1:29-31 includes a very long list of sins, all of which indicate the presence of God’s wrath, and which are almost certainly committed by a slave owner (eg heartless, ruthless!)