That reason provides the moral cover for mudslinging at the victim but we all know what's going on.
From the perspective of those around Rittenhouse, they had no knowledge if this was about to turn into a mass shooting or not. Disarming him may well have saved lives (and would've as it turns out).
Defenders of these "stand your ground" type laws ignore the consequences of cases like this. Here's the lesson from the Rittenhouse case: as soon as he pulled out a gun, someone else should've shot and killed him and then argued (with some justification, honestly) they were in fear of their life.
The extreme here is the case of Curtis Reeves [1], who started an altercation with another man who was texting during the previews to a move. When the man stood to confront him, Reeves shot and killed him and successfully argued he was in fear of his life.
Take that further: the victim can reasonably argue he feared for his life when confronted by Reeves so, if he had a gun, he should've pulled it out and shot Reeves dead.
Like, this is just absolutely bananas.
[1]: https://www.abcactionnews.com/news/local-news/i-team-investi...