I think there's a vibe out there in many cultures (including American) that being vegetarian/vegan or certain kinds of sympathy towards animals is unmanly and just kind of lame. This is probably more true in the right-wing demographic. I'm guessing this has been discussed in the animal welfare movement somewhere, so I won't attempt to delve into the issue further in this post.* Instead, I merely want to favorably acknowledge some commentary by comedian Bill Burr about boiling lobsters alive.
Bill Burr is a super-famous comedian and one of the most prominent cultural icons of masculinity in the U.S (perhaps in some respects the most prominent). Although I would say he is a party-neutral comedian, his comedic themes have included anti-wokeness and challenges to certain aspects of feminism, and probably has a huge following among working-class right-wing men.
Here is his commentary on boiling lobsters alive (6 min), excerpted from his podcast.
*Edit: Actually I will go into it for a minute. If anyone wants to see a great example of how to deal with this sort of thing in a different context, take a look at how Ford dealt with the issue of environmentalism/green-politics being considered soft, lefty, snowflake stuff when they wanted to advertise the fuel economy on their F150 pickup truck: "you won't be put in a chokehold everytime you fill up".
I'd guess that does still hold after adjusting, but I did take it out.
One thing is that I'd guess working class, rural people are more likely to work in some area at least adjacent to the meat/fish/food industry, and so the vegetarian movement would go against their livelihood, which might make them more likely to oppose it. To be clear, I'm not blaming those people. I think the city-dwelling meat eater who deliberately shields themselves from the unpleasant sight of the process that makes their food is much more troublesome.
Also, working class areas just don't have vegan food available as much.
I'm sure many farmers do care about their animals.