There was no placebo control group however. This summer the NIH will be starting a clinical trial which does include placebo and antibiotic arms that will hopefully answer these questions conclusively. Empiric therapy with antibiotics should be for at least 4 weeks. The fact that you don't feel better after a few days of antibiotics does not prove you don't have an infection. The fact that you feel better after antibiotics does not prove that you had an infection.
All antibiotics have side effects, most mild and self limited, some serious and permanent.
However, this identification of quinolones for particular vilification over other classes of antibiotics is misguided. I myself was hospitalized as a teenager for a complication from tetracyclines taken for acne. The indiscriminate use antibiotics with no indication of infection other than having the symptoms of CPPS is ridiculous, harmful and has no basis in scientific evidence. For antibiotic therapy, I prefer to do a culture and treat according to the sensitivities I find. All things being equal I prefer to use a quinolone because of the excellent penetration into the prostate.