> From my experience, bad evidence works wonders in arguments
It is because people have different goals and are using different metrics. They are just getting confused and thinking they are aligned with the same goals. If you are seeking truthful arguments with debates between good faith and purely rational parties, then weak evidence isn't great, because (like the parent said) it just creates a man made of straw than can easily be torn down. BUT if your goal is to perpetuate arguing and drive up emotions, the tool is fantastic. Because it creates a man of straw which can easily be torn down! Everyone likes burning a big man. I hear they even do it yearly out in the desert.
So people just aren't able to properly communicate because language is fuzzy and filling in gaps. That we're assuming those gaps are filled in the same way, but they aren't. Weak evidence is either very useful or very hurtful, but it depends on your settings and goals.