The situation
I am a male engineering researcher at a Canadian university. I recently had a conversation with one of my female colleagues who mentioned that she had a bad experience with one of our lab technicians. She didn't get into specifics, but mentioned that it involved sexism and that it made her somewhat leery of asking for that tech's help in the future. My reaction was, "Wow, that sucks. That's really not acceptable behaviour on his part."
I use this example to illustrate a point. I am aware that there is sexist behaviour that happens quite often in my field (engineering tends to be very male-dominated), but I usually only hear about it second-hand from female colleagues. To be clear, when I say sexist behaviour I don't mean criminal behaviour like sexual assault or harassment (although that does happen). Instead I mean incidents which, taken separately, probably wouldn't be considered a big deal but, taken together, are very demoralizing for my female colleagues.
Edit: Let's not debate whether or not the actions were/weren't sexist or did/didn't happen. I have not provided specific examples of what was said for this exact reason because normally they cause the answers to devolve into debate about what is the definition of sexism or "how far is too far".
My thoughts
Usually my response to hearing about this is, as above, "Wow, that sucks. They shouldn't have done that." But when I say this I wonder if it just sounds like empty platitudes. I don't think it is appropriate to confront the perpetrators, because it's none of my business (nobody is asking me to do this) and I don't have all the facts.
The question
So here is my question: in what ways can I support my female colleagues who experience repeated sexist behaviour in the workplace? (Other than not engaging in sexist behaviour myself, which I feel is a moot point). Specifically, how should I react to one of my colleagues telling me about this sort of thing? Again, assuming that I believe that the events did, in fact, happen and were, in fact, sexist.
Edit: Questions that I am not asking!
I am not asking what the company should do: this is debatable and would constitute a debate about proper company policy to protect workers. I am not asking what society can do: again, this is debatable and would constitute a debate about the true extent of the problem of sexism and what legislation/social action should be taken. I am not asking what my female colleagues should do: obviously if they feel threatened or face discrimination that makes it difficult to perform their duties they should communicate those problems to management.
I realize the answers to this question may be somewhat subjective. If you can back it up with personal experience that would be great.