For the theatre... mm. The thing with auditions for a creative work is that the director is allowed a lot of personal input. He or she is under no obligation to choose the objective "most qualified" or whatever - he or she could hire someone with no experience at all over a distinguished veteran actor/actress if the director was more impressed by the former at the audition. Since the director is hiring for his or her vision of the play/film/etc., which is not objectively measurable, he or she is under fewer obligations. In fact, it's considered quite normal for physical characteristics to be considered when casting a part, if they're relevant. As a basic example, most (though by no means all) productions of MacBeth would cast a male actor as MacBeth and a female as Lady MacBeth. Just as Hamlet will be cast by a young actor and Polonius an old, Hermia a short actress and Helena a tall, etc. This seems pretty reasonable to me, at least. It's just a necessary "evil" of the trade.
On the other hand, characteristics which do not show up in parts an actor plays, such as his or her religious beliefs or sexual orientation, do not appear to me to be fair game.
In other words, I am okay with "discrimination" in hiring if it can be reasonably showed that the discriminating characteristic affects qualification for doing the job, and with theatre/film there's a fair bit of potential here where there wouldn't be otherwise.
There's an interesting debate to be had on the Hooters subject about whether Hooters (and for that matter, more respectable restaurants) hiring "more attractive" is fair game for similar reasons. I don't know how I feel there.
For the life of me, though, I can't see how sexual orientation is relevant to... very many jobs at all. There's probably a small number you could make a case for (I suspect I wouldn't), but attorney certainly isn't one. Like religion, it's a pretty private thing.
The stripper case, I feel you nailed. You shouldn't be able to fire one for being old, especially when you can just take note of how popular the stripper is, and fire her if she, well, isn't.