De escalation is not commonly taught. Nor is it fully viable in all situations. It is important for self defence, but i haven't used that term for why i want to seek martial arts, since i came to the conclusion saying combat is better. (which is uncommon in martial arts to learn BTW, as they don't teach you scaling force usually, de escalation etc, you need to seek out specilist instruction or a uncommon type of school)
And the moral and judicial argument and elaboration of above is probably outside the scope of this thread as this is strictly about forms. Just in case what i stated looks like a borderline ToS break, all i will say is, so long as you have lawful authority to use violence in that situation its up to your own moral judgement if you do or not. (which knowing my typex, it looked greyzone to endorsing unlawful violence. )
And for self defence the first is paramount but read above. Both about my view on it and how the category of martial arts school, usually doesn't teach self defence skills to you. Wouldn't call it common, wouldn't call it rare, so its uncommom if they do. How ever there are some specialist schools which fall outside the martial art category i would say, which do teach you these skills.
I think Ramsey Dewy said something like(in relation to RBSD i think or bad MA):"they teach you how to face violence with wimpy violence"
edit: Martial arts and combat sports also help people with aggression, anger and violence issues also. varying amounts but it gives them a positive place to release it and help control it.