This argument frames women's exposure to sexist material as a matter of Choice. Sometimes it's even accompanied by attempts at pro-feminist logic like, "Don't women want choice? Denying them choice would be sexist!"
However, women should not have to make choices all the time about whether or not to be offended, marginalised, or belittled. It's even worse when the choice to avoid offensive content means choosing to avoid a community, a source of information on other subjects, or a field of endeavour. The "you don't have to read it" response sets up a double standard: freedom to not read or view something becomes an excuse for requiring differing amounts of labor from women and men in order to enjoy a conference or get technical information.
Telling women that they should choose what to consume and what to avoid is also a kind of Victim blaming, as it places responsibility on the people affected, rather than the people who are causing the offense in the first place.
In addition, sometimes women have to expose themselves to offensive material in order to see what they're up against when strategizing for societal change.
CouchDB: Perform like a pr0n star was a sexualized presentation given at GoGaRuCo in 2009. It consisted of numerous slides with scantily clad women, and content that talked about sexual topics including Viagra and the like.
When people complained about this talk, the presenter said that the title of the talk should have warned anyone who was easily offended, and that they could therefore have stayed away.
- "The topic of my talk was obvious, and I would have hoped that people who were likely to be offended would have simply chosen not to attend my talk or read my slides on the internet. It’s like complaining that television has too much material unsuitable for children, yet not taking steps to limit their viewing of it. You can’t have it both ways." 
The problem with this is that if a woman was attending the conference and wanted to learn about CouchDB, she would have been excluded from that opportunity at the risk of having to deal with a Sexualized environment. Worse, if a woman knew that Technical conferences were often like this, she might avoid them entirely, at cost to her career development.