I think it is quite close to Sci-Fi canon to treat aliens as a thread and go to the war. Every time humans make first contact, some sort of war happens. AFAIK, only Vulcans did not try to enslave/wipeout us. Well, may be Centurians too, but Minbari rectified it
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It is forbidden to kill; therefore all murderers are punished unless they kill in large numbers and to the sound of trumpets. - Voltaire