You just hit on one of the fundamental reasons why all online communities tend towards toxicity – the people who have the most time and energy to invest in discussions (which eventually snowball into flame wars) are the people who aren't actually doing the actual work.
These things then feed off of themselves – in a sociopolitical 'guardian' type community (/r/atheism, /r/childfree, etc etc) it ends up becoming highly caustic towards the outgroup with everyone competing for in-group status points, while in a 'trader' type community (/r/entrepreneur, /r/marketing), you end up getting flooded by shysters and self-promoters.
The moderates shake their heads and leave, and you're left with the inmates running the asylum.
These things then feed off of themselves – in a sociopolitical 'guardian' type community (/r/atheism, /r/childfree, etc etc) it ends up becoming highly caustic towards the outgroup with everyone competing for in-group status points, while in a 'trader' type community (/r/entrepreneur, /r/marketing), you end up getting flooded by shysters and self-promoters.
The moderates shake their heads and leave, and you're left with the inmates running the asylum.