Every social media (including this) is designed to grab attention of people, which is a well known fact. What we don't know is that they are designed to provoke each other as well.
When speaking the tone matters and it is easy to say offensive words without causing offence, but here even stating facts can get offensive as the tone is missing. Now the fast pace of communication makes sure that you might miss some nuances and it will be open for interpretation.
So this is a perfect disaster, now add karma points, up votes and blocking, it can get to your nerves. Examples:
1. Twitter: 280 character limit will limit the expressiveness and minimise the nuances that you can express. Retweet and trending will incentivise to brigade each other.
2. Reddit: Karma system and upvote with high mod privileges, makes it a cesspool where there is constant downvote brigading and bans. Reddit itself is poorly structured to say the least, driving away sane people out of it
Now coming to Mainstream media, It has a vested interest to increase their viewership and it is demonstrated that negative news will get more number of people attached to screens for more amount to time, downside is that people become hateful, but they don't care.
Politicians have a default state of spreading hate for vote bank, nothing can be done about it.
Finally consider this that there is decline is college enrolment (especially men), now college campuses are testing ground for ideologies and now it is becoming echo chambers, which means there is a kind of balkanization going on in the society. remember most of the political movements started in college and it worked out because general public had trust in those institutions, now it is not the case.
Now the hatred is so deep that one side wants to use army to attack their own citizens (biden speech). The other side celebrates the defeat of its own country in wars (afgan pullout, ukraine war). Although it is fringes, it is creeping into mainstream.
