A few things: It is not clear cut how the women are sitting. If the women were supposedly seated in the back, it should be obvious, but it isn't since there are women who are right up there at the front (see the left side) and some men are at the back. We shouldn't be compromising the shari'ah for the sake of learning. Also, we should not lay blame at the shaykh since he is not the management and he may have alerted the masjid management of the situation who may not have heeded but ultimately the blame lies upon the management of the masjid. Furthermore, Umar separated men and women because of the fear of fitnah. We are talking about the time of the sahaba , the best of generations, and Umar separated the men and women with a physical partition. In fact, he initially banned women from the masjid. 'Aisha also shared the same opinion.