Animal agriculture is especially worse because it plainly demands much more agriculture to happen due to it's inefficiencies. It requires growing huge amounts of animal feed where most of the energy is lost. Even it's best case is bad compared to the worst case for eating plants directly

Transitioning to plant-based diets (PBDs) has the potential to reduce diet-related land use by 76%, diet-related greenhouse gas emissions by 49%, eutrophication by 49%, and green and blue water use by 21% and 14%, respectively, whilst garnering substantial health co-benefits

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Plant-based foods have a significantly smaller footprint on the environment than animal-based foods. Even the least sustainable vegetables and cereals cause less environmental harm than the lowest impact meat and dairy products [9].

https://www.mdpi.com/2072-6643/14/8/1614/html

The FAO, unfortunately, has quite a history in downplaying things and sticking their thumb on the scale in favor of the meat and dairy industry on things like this

In a sign of the atmosphere in the FAO at this time, a fourth veteran insider, “Mary Wagyu”, claims to have been admonished after preparing Meatless Monday leaflets for distribution in the cafeteria of an FAO heads of state food security summit in 2008. “Remove and destroy them,” a senior FAO executive said, according to Wagyu. “These will not be put in people’s trays.”

In 2009 a second FAO report called Livestock in the Balance was delayed for several months while the FAO’s leadership tried to dilute references to harm caused by the meat industry, arguing that this had already been covered by Livestock’s Long Shadow. When the research team resisted the pressure, management stepped in and manually rewrote key passages over their heads, sparking what Steinfeld called “a mini-revolution”. About a dozen staff members involved in preparing the report withdrew their names from the paper in protest.

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Between 2012 and 2019, “the lobbyists obviously managed to influence things”, Holstein said. “They had a strong impact on the way things were done at the FAO and there was a lot of censorship. It was always an uphill struggle getting the documents you produced past the office for corporate communications and one had to fend off a good deal of editorial vandalism. You had to accept relatively small steps forward in changing the narrative on livestock.”

Steinfeld added that meat lobby representatives and diplomats would talk to senior FAO managers and encourage them not to invest in work that dealt with environmental impacts.

https://www.theguardian.com/environment/2023/oct/20/the-anti-livestock-people-are-a-pest-how-un-fao-played-down-role-of-farming-in-climate-change

Graph from the article:

Per capita beef consumption is down slightly, but not as much as chicken / poultry consumption has increased. People are generally eating much more meat overall per capita. Chicken and poultry still have a pretty heavy emissions profile, it's just that beef is somehow worse. The net increase in meat consumption is still a massive net negative on the climate

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In terms of ethics, switching to chicken results in significantly more induvidial chickens being killed because of their lower slaughter weight. The factory farms that house the vast majority of chickens keep growing larger and larger and quite disturbing. This is true around the world. For example just in England alone, there are at minimum over 700 factory farms for chickens, four of which have over a million chickens

Not sure I get the joke?