I'm going to convince my coworker to sign up for a pyramid scheme
Why would you want to get him involved in scam?
I him make to lose money and ruin his life.
That's a terrible goal!  People shouldn't try and con or deceive others like that.  If you don't like the person, just leave him be!
I'm bitching out of spite and to tarnish his reputation. Also, it's a game if this guy gets laughed at and shuts the fuck up.
Even if you have a problem with him it is wrong to scam someone. If he tells other people they might look unfavorably at you because of what you did. How would you feel if you were scammed?