why is arguing a bad thing?

so i was looking at his post:https://boards.na.leagueoflegends.com/en/c/gameplay-balance/d3YBaO7f-look-at-this-2013-video-of-scarra-on-zed-9-1-1-with-317-farm-at-28-mins-lvl-18-vs-lvl-14-vayne and the moderator locked it because it has "devolved into arguing.". isn't that a good thing? especially when the matters that are being discussed touches alot of people. people are going to agree and defend this position, while others don't. it never reached offensive language so i don't know why it has been locked
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