lesser function

Putting aside that this might be difficult to quantify, why do you think it matters? There are some groups of humans who exhibit severely diminished mental capacities compared to the average human (e.g. babies, severely mentally handicapped people, people in a coma, etc.). Would it be okay to eat them? Because I'm fairly confident that for whatever measure to compare cognitive functions you could come up with, we would be able to find at least some humans who perform worse on them than the average pig, for example.

different species

Why does this matter? As a hypothetical thought experiment, do you think it would be morally justified for us to eat aliens who are biologically very different from us but of comparative intelligence (or higher)? Or for them to eat us?

it’s the easiest, most accessible, most fulfilling, and healthiest way

Apart from the "fulfilling", which is arguably subjective, I don't think the rest is true. At least I don't see how not eating meat would be difficult or "inaccessible" in a significant way, and considering the last point studies regularly show that vegetarians and vegans are, on average, slightly healthier than other people if anything (which might be in part just correlation, but it does contradict your claim of meat being the "healthiest" way to get nutrients).

Fuck Tyson though, those bastards can go to hell.

On this we can definitely agree.