I think it's interesting that they're attacking things from the human/social side, but don't even mention the possibility of tweaking game mechanics.
For example, years ago I made a DotA-genre map for starcraft. The community was significantly less "toxic". This may have been due to its smaller size, but there were also game mechanics that I think contributed to it.
First, I focused on uneven games being fun. This was mostly achieved by (partially) shared income. On a smaller team your portion of the shared income was higher, so your hero was stronger. An ally leaving had upsides: suddenly you'd have a higher income and a bunch of back-dated income.
Second, dying had no downsides except you had five lives. You didn't get a time-out. The enemy didn't get experience or a pile of money for killing you. Instead, you'd repick your hero and spawn back at base right away. When you died you came back specialized for the current situation and you came back fast (you had constructive things to do; no time to focus on complaining). Until your last life, dying actually had upsides! Sometimes people would even strategically die, trading a life in order to switch roles or to teleport to the base (in dire situations).
It was hard to be angry at a terrible player for dying repeatedly... they were removing themselves from the game, after all. I'm sure the smaller team size, and the presence of 'safe' tasks like moving tanks to defend key areas, also didn't hurt. Having a weak player on your team wasn't ideal, but you could still have a fun game where they contributed.
I've played a few of these games, and I also think it's an issue with the core mechanics. Each match can be around forty-five minutes long. So it's really easy to dig a hole for yourself and spend a lot of the game getting repeatedly beat down. Then add in the high learning curve, and small teams. This means that a single player who's learning the game or trying out a new strategy can potentially cause his entire team to lose.
If you intentionally set out to design a game that turned all your players into assholes you'd be hard-pressed to come up with a better system.
For example, years ago I made a DotA-genre map for starcraft. The community was significantly less "toxic". This may have been due to its smaller size, but there were also game mechanics that I think contributed to it.
First, I focused on uneven games being fun. This was mostly achieved by (partially) shared income. On a smaller team your portion of the shared income was higher, so your hero was stronger. An ally leaving had upsides: suddenly you'd have a higher income and a bunch of back-dated income.
Second, dying had no downsides except you had five lives. You didn't get a time-out. The enemy didn't get experience or a pile of money for killing you. Instead, you'd repick your hero and spawn back at base right away. When you died you came back specialized for the current situation and you came back fast (you had constructive things to do; no time to focus on complaining). Until your last life, dying actually had upsides! Sometimes people would even strategically die, trading a life in order to switch roles or to teleport to the base (in dire situations).
It was hard to be angry at a terrible player for dying repeatedly... they were removing themselves from the game, after all. I'm sure the smaller team size, and the presence of 'safe' tasks like moving tanks to defend key areas, also didn't hurt. Having a weak player on your team wasn't ideal, but you could still have a fun game where they contributed.