The claim here is that lions, etc. would kill you, so it is OK to kill them.
Most animals we eat are herbivores, such as cows, pigs, sheep, chickens, etc. So the supposed reciprocating morality argument doesn't even apply, because herbivores wouldn't attack humans for food.
If a six-year-old is mad at you and punches your leg, you are not ethically justified to lay him out with a kick to the throat. Using superior might in this context is no different that using weapons on animals. It doesn't matter that they don't have the same moral compass.
Similarly, are we allowed to commit genocide against the Sentinelese because they attack anyone that approaches their island? Or what about combative dementia patents, can we line them up and use them for MMA practice? This starts to get kind of out of hand as to what is permissible in this context.
Most carnists would agree that you don't bite other people's cats, or bark at other people's dogs, even if they would do the same to you. So carnists don't actually believe this argument regarding themselves.
Eating meat comes with other impacts such as the starvation of food out of countries to feed livestock, as well as environmental impacts that hurt people. So this doesn't justify the collateral damage that comes with animal agriculture.