Not all youkai are immune to physical trauma. You could take down, say, a tengu with a lucky wing shot. Even a legendary youkai like Nue was said to be brought down by an arrow. At the very least, guns could make some of the factions treat humans more fairly.
Of course, I'm against our 2hus...
Marisa really does great in whatever she puts her mind to.
Also, who allowed guns in Gensokyo...? That's one crazy equalizer vs youkai if the humans mass-produce those.
Must be butthurt that all their gay games are flopping hard, and the usual sprinkling of liberal toxicity.
I'd just ignore them. We're here to enjoy Tomoko's antics.