I've taught and attended womens only classes since the beginning of my aikido career. Some with the teacher from Heart of the Mission Aikido whose link is provided in an above post.
Without opening an entire on-slaught of conversations about gender politics,etc.etc.etc......(snoorrrrrrre) , so please, let's not go that far, I will point out that many, if not most, dojo have nothing even close to strong womens enrollment.
These are broad sweeps of the brush and there are exceptions, but there are diminishing numbers of women practicing in many long-time dojo and the number of women coming to aikido and staying is pretty slim, too.
The dojo where I first trained and was a member of for many years has a strong womens showing,relatively. As does Heart of the Mission Aikido, as do all of the dojo in Heart of the Mission's 'friends' links. All of those dojo provide womens only classes and put awareness and attention to the presence of women in the school. They also offer beginning classes where a male and female student co-teach. This awareness brings about support. When we see people like ourselves we feel welcome. It is simple human nature. So gender politics aside the proof is in the pudding: THE WOMENS NUMBERS ARE HIGHER IN THE SCHOOLS WHO PROVIDE THESE CLASSES. Not that the schools don't have things to work out and not that other schools don't have strong womens showing. It's simply a matter of observation and asking the women 'did you enjoy that class?' and thy say 'yes' and they continue to train.
I'm coming up on 20 years in Aikido and I know I've been supported by this community approach.
In general, I support teaching classes with intentionality where a gap exists, be it male,female,racial,class, or culture. If you see a gap fill it with loving intention and good training.
Well, you know what the say about good intentions and the road to hell
There are even fewer African-Americans in Aikido then there are women, but I wouldn't support racially exclusive classes either, even if it did increase enrollment. Maybe I just don't believe that the end justifies the means.
Being encouraging and supportive, on the other hand, sounds good to me...