The waters are muddied and it isn't a clear case either way. If you want to argue about rape culture, look to the comic industry itself for the way it portrays women or the organizers of these events.
The problem is that many of the women in costume at these events are paid to be there and to dress provocatively. They are paid to do this for the express purpose of drawing attendees and generating interest. They are basically paid to be ogled.
You then have convention attendees that like to dress up, and they dress the same way the paid "performers" do. If they are caught up in the ogling, I'm not sure it is all the guys' fault.
Actually touching someone without permission or even catcalling aside, is this really sexual harrassment? It certainly isn't a clear case of "rape culture". Event organizers are basically paying women to get the attention they are getting. If anyone is promoting the rape culture, it is the event organizers, not the attendees. And that is not deflecting blame.
At an NFL game, is it sexual harrassment to stare at the cheerleaders? Is it sexual harrassment to take pictures of them? Hint: No. That's exactly what they are there for. Now what would happen if a woman attending an NFL game as a spectator chose to dress exactly like an NFL cheerleader. Would it be the guy's fault if they stared at her and took pictures of her too? Not sure how that would be the case.
Basically, I agree with mpfunk that we have a problem with "rape culture in society. I disagree that men staring at women dressed up as comic book characters at a comic book character convetion is an example of it.