Agreed that tube should not be plugged.That vent tube should not be blocked off. This is sometimes done when there's a crack in the drain tube that runs through the gas tank to stop it from dripping constantly. Not really dangerous but not ideal.
You may be getting some gas leaking higher up at another junction and it's mixing with oil/chain lube as it migrates downward.
Oil leaks can be hard to trace since the drip is often far from where the leak is. Clean up the bottom of the motor with degreaser and see if you can find the trail.
For particularly hard leaks to find they make UV dye you add to the oil. Then you ride for a while and look with a UV flashlight. Never used it on a motorcycle but I did use it on my 21 year old car and it worked great.
As stated above already, it could be leaking oil from somehwere up higher and just traveling down the outside of the vent tubes or even just oil/lube from the chain. Best thing to do in my opinion is to take the fairings off and spray the bike down with some Simple Green or an equivalent de-greaser clean her up real good, then keep an eye on some of the areas you found to be mostly wet or just anything that caught your eye while cleaning. I tend to do this yearly as general maintenance, I have a slight leak that I'm pretty sure was my valve cover gasket, just re-sealed it again and time will tell if that was the culprit or not.