I agree, and if one wants to speculate on why there are higher blood levels of O3 in those with prostate cancer (or other cancers for that matter), then it's important to understand what O3's help with - anti-inflammatory action. Cancer is an inflammatory condition.
Here's another example, sometimes low HDL is observed, but the underlying inflammatory condition that causes HDL to be low is ignored.
It's really easy to see how this study was set up, in a fairly transparent, contrived fashion (IMO, at least) to influence people away from omega 3 supplementation. As Kaladryn put it - only big pharma could be capable of such deliberate and possibly harmful persuasion.
Most things in moderation. If one doesn't eat fish, I can't see how a reasonable dose of quality O3 fish oil supplement will cause any harm greater than having some flounder, cod or shellfish daily (or some fatty fish ~2x per week).