Many hobbyists will recommend all-male tanks for several reasons, one is the amount of color (excluding Festae) the males contribute to the tank's overall appearance.
While Harems tend to be relatively peaceful I noticed a pair in a tank is much more aggressive and territorial than a male w/ several females....the harem mentality seems to "condition" them and teach skills for group-living, in a word.
The hardest part about all-male tanks is dominance and the struggle for it that is to be - you as the keeper have to play close attention to the hierarchy and 1.) make sure there are enough males to keep them from putting too much focus on any ONE fish - so while 2 may not work, 3 might be the magic number and so-on.
In my experience aggression can be managed by overcrowding (Yes, overcrowding - I said it) .....and if you scan through some threads of people w/ with "Community" cichlid tanks, you will take notice almost ALL of them have more fish than the "1inch of fish per gallon rule" suggests....
Many members here on MKF are orthodox, and a few like myself are quite unorthodox, but I have also accomplished many things this way that orthodoxed keepers have yet to achieve. I'm not saying "break" the rules per say, but you can certainly bend them a bit if you know what you are doing and don't mind putting in the time ad effort to observe and move things around when need be