I think someone would see more success convincing people to eat less meat rather than eat no meat. e.g., make red meat a special occasion thing rather than an almost nightly occurrence.

This could work a little at a personal level, but any larger campaign is going to come up against industry groups with more funding and no financial reason to care about much of the environment.

I don't know about the US, but in Australia, there are very strong campaigns promoting lamb consumption, for example. It's tied very effectively, through marketing, to our national identity as part of Australia Day.