If you want to respect the actors, watch the show without disturbing them or the audience and respond appropriately to the performance. The actors are getting paid to perform every single show to every person in the audience, regardless what the audience is wearing and 95% of the time, they're not even supposed to notice the audience until curtain call, much less try and see if someone's legs are fully covered when they are sitting in their seats. I truly do not understand this weird equation of LONG PANTS = RESPECT FOR ACTORS comes from. It doesn't make sense at all.
And if you aren't enjoying the show to the point where you are uncomfortable wasting your time, then leave. Preferably, during intermission (if there is one), but any time you wish is actually appropriate. Purchasing a ticket does not commit you to being held hostage to endure the unendurable because someone once said on a message board that you owe it to the cast as a sign of respect. It's not true.
"What can you expect from a bunch of seitan worshippers?" - Reginald Tresilian