Paul spoke about singleness a lot (and that's why the Pastoral letters where he endorses men getting married is a sign that the letters are fake). Many gospels that didn't make the canon talked about abstinence even in marriage.
Seeing as believers tend to believe in God wherever they see it, in "a God of the gaps" in their knowledge, it might be too easy to say these people saw things like syphilis as a sign that God hates sex.
Or perhaps they were trying to show the Romans that they weren't into orgies as they were so accused. Whichever.