Question

How do you write an persuasive argumentive essay when there is only one opinion?

Answer 1

You're typically supposed to have three but this case says otherwise. 
you're going to have to try and break those down into 3 sub topics.
When you've done that you have to:
1. Support claim with evidence. You have to find lots of evidence and fact to support your claim.
2. Present sub-points or arguments to help your claim get into the reader's mind.
3. You have to acknowledge the opposition because every claim has one. You have to disprove the claim and make your readers think it's wrong.
4. Be clear, be informative, tell the reader the connection between  evidence and claim (only if it isn't obvious), and never accidentally support the opposition because readers can easily spot that.