Consider these points:
“We should outlaw all weapons everywhere in the world” – too broad; you can’t convince us of that in a single speech or paper.
“We should not let John Norland use power tools, let alone guns.” – too narrow; there’s not much to say after you’ve stated the thesis.
“We should oppose (or support) any concealed-carry law in Rock County” – good; you may convince us of this.
Trying to convince your friend to join the Peace Corps is too broad; getting them to attend an informational meeting with you is achievable.
Describe one instance where you were presented with an argument that was so broad that it was not achievable OR one instance where you were presented with an argument that was narrowed so it worked.