Women need to able to voice their sexual desires without shame.
And this nice, positive statement is completely negated by the last sentence in your first para.
Surely the message should be, 'as long as it's something you want to do - and [of secondary importance] if you (both) prepare properly, it should be ok'.
Because the statement the way you frame it is negligent, and certainly doesn't encourage young people to 'voice their sexual desires', as you say.
Perhaps you think the 'as long as you want to do it' bit goes without saying - but it clearly does not. It needs to be explicit - this is what we need to be telling all young people, loud and clear, repeatedly, boys and girls.
It's not good enough to hope the message gets through implicitly.
If I, as a teenager, heard an adult in a position of authority simply saying, 'as long as you prepare properly', I'd be taking it as, this is something I should do / I should feel able to do / I should be willing to do. I wouldn't feel good about that at all.
Some women want and enjoy anal sex. And that's ok.
Not one reasonable person on this thread is arguing otherwise. But you are missing out a whole part of this equation.
Some women don't want, and don't enjoy it. And that's also ok.