silly hypothetical: self-defence for spitting?

hi everyone. Posting here because I can't post hypotheticals in r/legaladvicecanada so I hope this is ok. I just saw a distressing video online about person A spitting on person B after a disagreement and it got me thinking: would person B have been well within their rights to hit them back in "self defence" since spitting is technically assault? TBH I don't know what is considered self defence in Canada/Ontario, but I just know that if someone spat on me I'd want to beat the shit out of them. Can the victim do anything in this circumstance except file a charge?