Show the structure of an evidence-based argument as a visual chain, and make the poster itself do the teaching.
The argument bridge
Draw the response as a bridge: ISSUE on the left bank, ACTION on the right, and the EVIDENCE as the supports holding the span up. An action with no evidence "support" visibly falls down. Students sketch their own bridge before writing prose.
Colour-code evidence vs opinion
As students read the source, they highlight facts/evidence in green and opinions in amber. Only green can become a bridge support. This makes the evidence/opinion distinction visible on the page.