I find it fascinating that as soon as vegan diet option is up to conversation, people just presume cuisine, cooking and recipes are thrown out of the window. "eat boiled beans with rice", is like claiming all there is to meat is to rip the package open and chew on raw meat with no seasoning is the default way meat is consumed, and make a case from that presumption
The are/became vegan, not Gollum that claim everything should be eaten raw to Sam.
Your point is well taken; I recognize that there are many ways to make beans a staple protein without being a tasteless mush. I am just not sure that every person who says "just eat beans instead of meat" is considering that at the time. Both "meat" and "beans" are obviously reductive, so I can only guess there's some assumption that the reader/listener will adjust accordingly... but it still gives me strong classist vibes when someone associates low wealth/frugality with beans.
The are/became vegan, not Gollum that claim everything should be eaten raw to Sam.