When you can't find any native speakers to back-up your interpretation of a phrase, it's time to leave it. That interpretation of scumbag is in your head, not anyone elses. Scum isn't slang for semen as far as I know, and bag isn't slang for vagina. How big a sample of far flung native speakers do you need?

You appear to be attempting to resurrect a previous argument for no reason in the face of the facts. That is trolling. Stop it.