system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] How do the Sith justify suppressing/ignoring their passions when they become inconvenient?

    Peace is a lie, there is only passion.
    Through passion, I gain strength.
    Through strength, I gain power.
    Through power, I gain victory.
    Through victory, my chains are broken.
    The Force shall free me.

So peace = bad, passion = strength = good. Ok basic Sith stuff and it makes sense. Now lets say this Jedi has really **really** pissed off some Sith Lord. The Sith knows he can kill the Jedi and is about to do so. 

However the Sith then finds out that the Jedi has been fed false information, if he is allowed to escape he will spread this 'knowledge' and inadvertently help the Sith. In letting the Jedi escape, the dark lord is acting in a calm and rational manner for his best interests and is actually suppressing/working against his anger. This seems at odds with Sith philosophy. 

Expanding on this, Darth Sidious managed to conquer the galaxy but used logic and reason to do so. It actually seems his success was in spite of his dark side connection to an extent, since he was at risk of the Jedi discovering his nature. Presuming he hates the Jedi then surely he was suppressing the thing that gave him all his power everytime he worked along side them calmly and peacefully.

How do the Sith justify this and why doesn't it affect their abilities?
gpt
Letting your emotions control you is a weakness any respectable Sith Lord purges early on when training their apprentice. Uncontrolled rage has its place, but a Sith who allows him or herself to be controlled solely by their emotions is a liability to the ultimate Sith endgame, total control of the galaxy.