Ignoring the jokes in the comments, this whole fight is really pretty and symbolic. Having an enemy whose power is to use your own past to injure and capture you, and to defeat him you have to "kill yourself" (As in kill your past self, to have a new life). This becomes even more evident when you realize this kind of "suicide" is a central part in Christianity. The "purifying water" may also be an allusion to baptism.

To achieve the ultimate power you must shoot yourself

Johnny: oh hi jesus I’m kind of in a fight rn ttyl (:
Jesus: shoot your self

Jesus told me to kill myself

Jesus promotes suicide, now that's new.
This stand is too broken, it needs to get nerfed.

Soooo was the civil war user on the confederate side or the Union side???

Jesus: Kill yourself, Jonny, you pussy

ok then i will not shoot onto nxt chapter

jesus is my waifu

do you have a minute to talk about our lord and savior johnny joestar?