While its true some can be or are labeled as more aggressive then other cichlids. I think it boils down to proper and responsible stocking, good male/female ratio, plenty of hiding spots, large enough tank with some open space to swim and do there thing and a good cleaning schedule. Keeping parameters in check and good food also will help keep them happy.
I've learned from experience that ANY African cichlid can become aggressive even becoming hyper dominate and claim the entire tank and kill 20+ fish.
I guess what I'm saying is this... Every tank is different and every tank will have there own personality. With these fish you never know.
I've had my share of issues by improperly stocking my 75 gallon so of I can stop someone from going through what I went through then I've done my job.