The amount of methane emissions from all beef agriculture today is within a factor of like 3 of the natural methane emissions from American bison prior to colonization of the Americas.
All of these analyses completely ignore the base rate of methane emissions in the absence of cattle, whether from preexisting natural ruminants, from e.g. the fungal decomposition of plant matter that would have occurred on grasslands anyway, or from "meat substitutes".
Even if the methane emission was 10x the absurdly inflated figures that anti-meat extremists try to claim, it would still be overwhelmingly worth it for me to consume it for the health benefits. It would be better for society to spend Manhattan-Project-plus-NASA levels of our GDP on methane catalysis/capture technology, if it were actually necessary, than to stop eating ruminant meat.