If you're wondering why I'm sporting a hard-on in this video for no apparent reason, it's not because I'm sexually attracted to housework (although it is more fun to do naked). This was the third take; on both of the first two takes, I splashed soap suds on my penis, and the coolness and wetness, coupled with the rubbing motion of rinsing it off, contributed to the erection you see here. There's nothing specifically sexual about it - I wasn't engaged in masturbation, and I wasn't even doing it to show off in front of the camera (as I've been known to do); it just kind of happened.
There's nothing indecent or threatening about "incidental" erections like this one, and there's no reason why they should have to be covered up. It's just basic human (specifically male) physiology. You don't even have to bring up its sexual role if you're explaining it to a naive observer - you can just say that a man's penis sometimes grows and stiffens and stands up. There's nothing alarming about that. It's a fact of life. If the mere sight of a phallic object leaves you in hysterics, then you need help - because that's not healthy.