Timmy is lucky to have a parent like you. I went through a similar phase where I started closing my door all the time because just like you, my mom taught me there are things that it's just not appropriate to say/do/watch in her presence so I shut her presence out in order to do the fun things I wanted that she deemed inappropriate.

Sadly instead of rolling with it and trusting me to make my own good choices my mom just outright removed my door for a year and did not allow me anything to cover it so outside of being in the bathroom I never had any privacy from her if I was home.

I'm not a parent, but I grew up with arguably a very bad one. You seem to be doing a very good job of being the parent in charge while still allowing Timmy the freedom to make his own choices and be who he is and that's truly wonderful.