Why did Rojan get banned?
That seems awfully loaded
Regarding Rojan, IS-2 and a couple of other fellows here on this forum, I'd dare say everyone is better off without those people and their toxic attitude. By the way, its not unusual for the majority of the "ranked" gamers to be that toxic, check almost every other forum of somewhat competitive games (or the old ones like wargame and ruse) and you'll find those people. If the community is large enough, you can mostly avoid them, if its well moderated they get banned pretty fast, but in small communities they are extremly bad.
I really like the decades old 1d4chan definition for those people, stemming from the good old times where strategy was played solely on tabletop (even back then those people were annoying as hell):
In wargaming: powergamers are less likely to be referred to as such due to its association with level-scaling systems, and are typically referred to as "tourneyfags" or merely "competitive players" which are generally neutral terms. Powergamers are especially hated in the wargaming community as they typically exude a noxious odor, have no interest in fun besides their own and are the number one reason people new to the hobby ragequit immediately.
A somewhat milder term with a similar meaning is "optimiser", which generally lacks the negative connotations of powergamer, in that they won't typically suck the fun out of anything they touch.
Edit: For everyone interested in this, I highly reccomend reading the rest of the definition on 1d4chan since it more or less describes what has happened here (see the 10vs10 discussion as a reference) and why SD is struggling so hard with new players: Hint: History repeats itself