Do you know exactly why the first man was chasing Kyle?
Let's go with your initial assumption shall we that Rittenhouse was 'waiving his gun' around (bear in mind open carry is legal in Wisconsin), does that give someone the right to chase after the guy carrying the weapon and act in a threatening manner to them?
I think your definition is self defence is certainly illogical but that's irrelevant.Also, there is nothing illogical about what i have said.