Matthews answers that the Lena image is a part of Computer Science culture. Lemire answers that there is no benefit to using the Lena image above other similar images, but there is damage since it offends some people. Neither argument is convincing. Memes like Lena shouldn't be actively encouraged since that would corrupt their natural propagation: Lena (and its origin) would be forced in front of people rather than discovered, and would be resented for that. Meanwhile "Getting Along" (Lemire's usage) sounds more like kowtowing and is not how CS prospers. CS prospers by being accessible, open, inclusive, and exciting, not by shaming members over moral trends. Resources are abundant, and Lena is not so pervasive as to obstruct participation.
Computer Scientists should use whichever images they personally enjoy, since they're the ones seeing those pictures each day. Anyone else can and should be offended as much as they are at any other poor coding practice.