Is it okay...
Is it okay to report two people for being toxic to one another? No toxicity was thrown directly your way. Muting them both would be the right thing to do if you were the type of person to be so anal about the rules that you would report two people for arguing. People either do dumb stuff that gets them reported while others sit back salivating for the chance to report someone. It's almost like we play for the report.
I know your first thought is "well they are disrupting my game and I king of all lol should never get interrupted, that's what Riot says!" and "Toxicity is toxicity no matter what form it takes"
come up with something new.