Sure we are trying to push people on some form of more sustainable eating, we're just worried for our common future and the future of our children. If we care about what others are eating or doing it's because there is only one planet and it is shared !
We can get a much smaller footprint through veganism, vegetarianism or flexitarianism, just less (much less) red meat is already a dramatic improvement. What is very strange for a non anglo-saxon reading some people there is how clear cut are all opinions. You're either a pure vegan (insect burger at worse !) or a big cattle eater, at least through the lens of some posters.
If we want to share an enjoyable planet with future generations we have to make more sustainable choices which does not necessarily mean living in full autonomy eating only beans.
We should just look at the big picture. Whats is producing 80% of our greenhouse emissions ? Can we live a fine life while replacing those thing/product/activities with enjoyable alternatives ?
It's a triathlon forum so performance should be addressed. I would certainly not sacrifice the planet for my amateur triathlon performance but having, read, studied, and experimented i don't think you really have to make any compromise on performance regarding eating.
All variety of protein can be covered by plant no problem, just mix cereal and bean and you're not that far from great. Also chicken and egg really are pretty efficient from a climate perspective. Some supplement can be good. There are so many solutions !
If one is very cautious a blood test is always a good idea, vegan or not to check if any supplement or change in a diet is needed.