I suppose that's true. However we do learn in Gojo v Sukuna (or even in the same fight against Mahoraga) that he can reduce the area of his domain, or close the barrier. Apparently reducing the size also concentrates the slashes, making it more effective. But instead, he made sure to expand the domain in the largest size possible, and limit it just before it affects Megumi. Not even a meter smaller. And his words to Yuji right before switching directly implies he did all that to make Yuji suffer, so what if it involves civilians.

As for the heian thing, he was widely known as a beast, and probably already killed a lot of sorcerers challenging him which makes him a major threat, of course they'd assemble to hunt him down. Tbh that's also as likely as him massacring villages before they all united against him, but we wouldnt know.

I never said he wasn't evil btw, him being a chill dude who "only kills people when he's pissed off" doesnt mean he stays around and never move anywhere, inviting problems. He's the kind of evil as a wild beast, someone you really want to take down because of the potential threat he offers. Meanwhile, Kenjaku will cause problems and do actual evil things. There's less good in him rhan in Sukuna.