"If someone's house is on fire, in this universe, it's a reasonable assumption they'd rather their house not be on fire. Somebody who respects them and is friends with them, if they don't know otherwise and they have a relevant spell, will put out the fire; if they're a stranger, they might put out the house fire on expectation that they'd be owed a corresponding favor. Even if the house-owner in fact really wanted to set fire to their house, they would usually know, they ought to know, that other people would incorrectly assume they didn't want their house on fire, and should therefore believe that somebody putting out the fire was probably trying to respect their incorrectly guessed wants. If the house-owner doesn't seem to get that, and yells angrily at somebody who put out their house fire, everyone else in this world knows what the common assumptions are that a reasonable person would make, so everyone else thinks the house-owner is being unreasonable."
"If you set fire to somebody's house, reverse all that; most people don't want their house on fire, and everyone else will think you were supposed to know that."
"If it's just a campfire instead of a house, reverse and the stakes are lower. Somebody with a campfire probably wanted there to be a fire, there, and damping it with Water would be an act of disrespect, but one with lower stakes than setting a house on fire."
"I'm walking through all this because it seems like a classic case where the Summoned Hero comes in with very wrong assumptions about what everyone else in the world assumes, and gets bitten by that, or if they're more powerful everyone else gets bitten by it. It's standard wisdom in this world - maybe not in yours - that above the physical Creation of affinitied mana and materials, there's a second Creation, the Social Creation, that's maintained by a rut-in-reality worn inside our minds of assumptions about what other people want and believe and our beliefs about what they should've known. It's not real the way that fire is real, but it's at least a little real and you're from outside that version of Creation too."
"Here, putting somebody's feet in acid is something they probably don't want, which everyone else will assume they didn't want, and will think you should've known they didn't want. And the most important fact I'm trying to convey - because it looks like it was different where you came from - is that it will be considered a big deal rather than a small deal."