If you don't like guns, and someone suggests adding guns, a sane, proportionate response is "I would not like guns." You could list reasons for why they wouldn't fit in with the setting. You could cite lore. There are a lot of things you could do actually. I think for the most part the responses to the thread tried to be civil and constructive, to varying effect.
But if, like certain members of the Story Team and its associated magic community, you have a festering persecution complex "spearheaded" by one guy, you lose your absolute **** every time they're mentioned. Your pupils dilate at the sight of [Lore] Musketry, your capillaries contract, draining the color from your skin. You begin visibly sweating as you write write "NO NO NO," and then paste the link to your group chat so your friends can upvote you saying "NO NO NO."
If you are in the "fantasy medieval aesthetic" community on this server you have no reason to believe your roleplay is being squashed by anyone. You have been repeatedly backed up by the administration. There are half a dozen independent nations and settlements catering to your ostensible taste for medieval roleplay. If you choose to see other people's lore proposals as a threat to you, you own the responsibility for it. No one else is the villain here.
I don't think Hanrahan is a very diplomatic man, but I don't ever see him "bashing (anyone) with toxicity." I think the guy can get emotional at times but it's hard for me not to sympathize with him; people seem to be offended by his persistence more than anything. I was even willing to believe that he had been toxic on the Musket thread until I actually went and read through his post history, which was entirely civil. Do better.
We can argue on whether posting [Lore] Musketry in the wrong format was destined to create a shitstorm, but Hanrahan bears almost no culpability for the unhinged, disproportionate, frankly whiny reactions from the community.