He doesn't swim naked, so he takes the summon anyway.
Can he say 'I do not intend to kill you unless -'. Or 'you can live if you cooperate'. Or something.
Sentences such as the following begin to come clear:
"The others will destroy us!"
"They will destroy the planet!"
"We are befouled already!"
"I am frightened!"
"We are unclean!"
"I don't want to die!"
"I don't want you to die," Cam asserts through his translator. He is pretty sure the promises police will not come after him for not incorporating the conditional.
"I want you to talk." He pats his computer. "This can talk to me and it can talk to you. Talk to me."
It tentatively peers out of the building where it and the others are cowering.
"Terrifying filth creature, I am [untranslated phrase, probably a name]. [More untranslated speech]. Please do not kill us. We don't know what you want. We are very afraid."
They really don't have any other words they've used for non-evil-alien-people besides "filth creature", do they.
"I want you all to stop killing filth creatures," he says.
"Please do not befoul us," says the spokes-alien. "Although the [same untranslated plural noun] will likely kill us anyway."
"[Untranslated adjective]! [Untranslated adjective]! We're [untranslated adjective]!"
"Shut up [profane intensifier]!" says another alien to the one who thinks they're all [untranslated adjective]. The adjective-wailer subsides.
"The end of the world!"
"Shut up [profane intensifier], [probably a name]!"
"Shut up [profane intensifier], [name]!"
"Nothing else has stopped this filth creature, why would destroying the planet even help?" someone wonders.
"Tell that to the [same untranslated plural noun]!"
"You tell them!"
The spokesalien has nothing more to add at this time.
"[Untranslated] is the opposite of filth," explains the spokesalien. After a bit of digital hemming and hawing, the computer renders its next sentence as: "The purity-keepers maintain purity so that no one is contaminated by filth. This is the most frightening colony planet, because of the filth contagion, but until today there had not been an incident in many thousands of years!"