When I was a child my mom once walked on me masturbating. She seemed very disturbed and interrogated me: what was I doing? why? who showed me that?
It's only later that I understood she thought that a child my age was normally "innocent" so I could have been somewhat "corrupted" by a pedophile or something.
She seemed puzzled and eventually left after reminding me that I should not do it in public (hey, SHE had entered my bedroom without knocking, otherwise I'd have hidden my erection).
How about you?