Thank you for the references. This response may seem nit-picking at first, but I way to honor your taking the trouble to provide references by providing a serious response, and also I think it is important to fight public misconceptions and moral panics, so here goes.
I got one hit on Google Books, zero on Google web, and zero on Google scholar for your quotation from "repeatedly cited" Elina Haavio-Mannila, whose wikipedia page is only available in Finnish, which I find surprising for someone being used used as an authority on a subject of such universal interest.
That quotation from Haavio-Mannila, "if local norms are more permissive with regard to sexual behavior, sexual harassment is more likely to occur", does not necessary even support your claim tht "showing reasonably mild sexualised images at a conference results in a statistically measurable increase in the number of sexual assaults carried out by participants", since showing an activity does not necessarily indicate that that activity is the local norm. Come to think of it, the opposite can be true. Quite often an activity is interesting enough to show because it is the not the norm, such as a news presentation. I think it's fair to say that a common theme among the other images in mark's presentation was that they were showing images outside of the "local norm", so the inclusion of an image in that set does not imply that is is the local norm, and would not, by the logic of Evina Haavio-Mannila's statement, necessarily make sexual harassment more likely to occur.
Moving to your second reference, the link to the abstract that you include only describes sexual jokes as making subjects more willing to confess, which is different from making people more willing to commit an act. Just to illustrate with a speculative scenario, it's not entirely implausible to me that seeing something made light of might make one feel revulsion, think introspectively about it and be more willing to confess as a path toward self improvement.
So, I'm not convinced yet that "there's various pieces of work that indicate that there's some level of association" for your claim that "showing reasonably mild sexualised images at a conference results in a statistically measurable increase in the number of sexual assaults carried out by participants."
However, I am digressing with this argument. As I acknowledged at the outset, you did say that you "don't think it fundamentally matters", and what I really objected to was that you then made an utterly untraceable reference to try to support your claim. It is important to me to reduce attempts to make vague untraceable references to authority, which I see as argument by intimidation, which I suspect contribute to public misconceptions (but I don't know of any studies to support this).
Anyhow, thank you very much for providing references. Even though I find the references unconvincing so far (maybe I need to go read Havvio-Mannila's book), your proving references of any kind has substantially increased your credibility in my view.