English Translation
They’re the enemy.
Vihollinen in singular is wrong. It should be plural partitive, vihollisia.
By the same argument, the english sentence should be “They are enemies”. But there’s a difference between “enemies” and “the enemy”.
Yeah, it is one of those sentences that just doesn’t map well from English to Finnish. I am not sure whether the English could be improved but the Finnish certainly has to be fixed so that it is grammatically correct.