Michael St. Jules posted a link to this post on Facebook and I wrote a reply (formulating it rather quickly I might add), and Peter Hurford suggested that I should copy and paste this reply as a response on the EA Forum, which I am now doing. These thoughts were hastily formulated and are highly fallible and critical feedback is entirely welcome.
" Thinking about the future a million years from now, moral circle expansion is clearly an extremely important concern (failure of moral circle expansion could be catastrophic, and could have catastrophic negative consequences both in terms of causing harm and failing to prevent harm, with each one of those by itself outweighing all gains to positive human well-being, under any plausible non-speciesist moral theory).
Achieving moral circle expansion earlier on plausibly has positive flow-on effects which exponentially grow over time, since if the attainment of complete non-speciesism by the human community occurs one day sooner, then the harm thereby prevented may be such that under other scenarios harm not prevented would have exponentially grown. So, one million years from now, positive flow-on effects from achieving moral circle expansion one day sooner could be significant. So a very strong imperative to work on moral circle expansion as soon as possible right now, including psychologically undermining one's own natural tendency towards speciesism and signalling to others that one is doing so, as long as there are no substantial costs to doing so.
Costs of being vegan are in fact trivial, despite all the complaining that meat-eaters do about it. For almost everyone there is a net health benefit and the food is probably more enjoyable than the amount of enjoyment one would have derived from sticking with one's non-vegan diet, or at the very least certainly not less so. No expenditure of will-power is required once one is accustomed to the new diet. It is simply a matter of changing one's mind-set. The flow-on effects of signalling a strong commitment to non-speciesism to those in one's immediate circle are highly positive. Some complain that one must pay a social cost. Sure, I found that too at least at first, but twenty years later my friends all highly respect me for sticking to my guns. In any case, the fact that there is a social cost to be paid is precisely the point: this is the thing that must be fought against. The tables need to be turned so that it is meat-eaters who feel on the defensive.
From long-termist considerations, the case for going completely vegan starting today, for almost everyone, unless you have some significant reason to believe you would be at risk of major health problems (which is statistically rare indeed), is very strong. "
Full disclosure, not in original FB post: Over 25 years of being vegan, I have occasionally, like Brian Tomasik, deviated from full vegan purity and been just lacto-vegetarian for a while. I now think that this is on the whole not justified.