Would you give treatment to a male patient with subjective dysuria but no objective pyuria with Ureaplasma urealyticum detected by PCR from urine?   

No treatment is indicated. First, dysuria alone in males is not an STD symptom; published research is clear that discharge is required to suspect urethritis. The absence of urine WBCs (i.e. no pyuria) is a pretty good substitute for examining for discharge - not perfect but makes urethritis unlikely...