In this instance it means that other people did not approve of what the women were doing. So they "looked down on them" because they believed they were better than the women on the stage. In general the phrase is used when again people are doing something or are something or are someone you do not approve of or think is beneith you. Basically if someone thinks they are superior than someone else they look down on them.

I couldn't agree more.That's why I couldn't identify that construction.

Just a grammar point to add here: This isn't a brilliantly written piece, and it should have the word 'them' at the end. Without 'them' you would have to read the sentence as 'Some said they were (unladylike and looked down on)' . Here 'looked down on' would have to be seen as a passive-style construction used adjectivally. This would suggest that these people said that actresses were 'looked down on', as if it were their opinion that others looked down on them. In fact it would be more logical to read this as 'Some people (said they were unladylike) and (looked down on them)' ie these people considered actresses to be unladylike and so they looked down on them. That makes much more sense, doesn't it?

I didn't know that actresses were seen as one step below courtesans and one step above prostitutes.Thank you for explaining the origin of this expression.

In those days the aristocracy sat in boxes at the theatre and looked down at the stage and the pit - where the lower social classes sat. This is where the expression- looking down on someone- came from. it had a literal meaning, that was then applied to social standing.