When I was young someone told me something similar (but not exactly the same) - "imagine you have a zip on your mouth and you have to unzip it before speaking". The point was not the zip, but to take the time to think before speaking rather than just saying the first thing that pops into your head.

Social media not only removes that moment of reflection, but it actually spreads explosive verbal diarrhoea. The commercial platforms are incentivised to encourage conflict and divisiveness because it drives traffic therefore profits. If everyone was encouraged to be nice and friendly on social media, people wouldn't spend as much time on it, so less eyeballs on ads and less profit.

I don't think that is the complete picture though. Having spent some time on alternative platforms that don't have the profit motive, I have noticed there is still a tendency for many people to be slightly outrageous, presumably simply because it attracts more engagement, and those sort of people like the attention. Say something sensible and you're not going to get loads of people replying "I agree", so after spending a lot of time writing sensible comments you end up wondering if anyone has actually even read them and you start to think - what's the point?

I wonder how (or even whether) you could design a platform that encourages sensible and penalises outrage.