it's not even controversial just nobody points at the known set of enzymes in human digestive systems. they don't fully decompose gluten (and are poor at many forms of casein, also not great at zein) and in fact specifically incidentally cut up gluten where they do manage to cleave it, to form peptides that interact with the endorphin systems, as well as being triggers of immune reactions when the mechanical abrasiveness of the protein opens holes in the intestines, allowing those peptides to leak directly into the blood.

the enzymes we have are keyed to meat.

even egg white is poorly decomposed. the acid and alkali in the stomach and intestines, respectively, go some way to attacking every bond in the proteins but are not strong enough to do what you get in a laboratory with higher temperatures.

it's not ideological, it's grounded in physical, biochemical reality that humans' main diet staple should be meat. fish and ruminants. fish proteins are very easily digested, softer even than ruminant/ungulate meat.