A persuasive speech needs one arguable sentence — and that sentence tells you what proof you owe. Sharpen it on the left and watch the type change. Then find out where the room actually stands and drag your ask along their belief spectrum: too far, and social judgment theory says they move away from you.
1 · Sharpen the proposition
The topic you were handed
What do you want them to accept? — this changes everything downstream
Sharpen it
2 · Where the room actually stands
Your ask — how far from them are you asking them to go?