I'll admit that I lack understanding, since I've had little contact with this problematic. Personally I feel more agender, but can pass as cis for the purpose of bathroom usage, so haven't had anyone question me. I also have little sense of taboo, so if anyone actually were to ask me about my genitals... I'd just answer point blank, and probably in more detail than they wanted to know... but you're right, it's really nobody's business. And totally agree on the assault part.
So what's your opinion on what would be the best solution, having non-gendered bathrooms with all the appliance options?