Yes people get stressed out. which is why the IFS doesn't punish people for having an off-game or two if they're not normally toxic. It's only when they make it a habit of being consistently toxic that they get punished. From Understanding the Tribunal:
4) That player in my game was far worse than me. Why am I banned???
a) I'll keep this one simple: retaliation isn't OK. Reacting to a toxic player by being toxic just incites that player to be even worse--it also ruins the game for up to 8 other players. It is far, far worse to watch two people yelling at each other all game than it is to watch 1 player ranting into blank space. Almost everyone in the game can find someone out there that behaves worse than they do--but so what? Finding someone worse doesn't justify your behavior or justify retaliation. We expect more out of our players. What players often don't realize is... those other players in your game that you thought were worse? Nearly 100% of the time, those players were banned even before you were. If someone is being toxic, just report them and move on. If you retaliate, both of you will be banned. It's really that simple.
If muting everyone at the start of the game is what it takes for you not to be a jerk to others though then so be it.