Look I'm pretty sure I already had it

Possible, and if so, not getting vaccinated seems sensible. But how you can be "pretty sure" about it, especially since you are arguing that it is easy to mix up with the flu. But if you took an antibodies test and you got a positive test for covid antibodies, then this argument would be a lot stronger.

B: "You said the vaccine works, so how am I supposed to make people sick?"
A: "It might not work perfectly, or their could be variants."

A should have pointed out: 1) many people won't take the vaccine out of fear generated by misinformation and, even worse, 2) some people cannot take the vaccine because they are already immunocompromised (and these people are the ones who would be at greatest risk of dying if you expose them to the virus).