How does Orwell portray Squealer in a negative light when he retells the story of the Battle of Cowshed and explains why Napoleon sent Boxer to the knackers?

In Chapter 7, Squealer tells the animals that Snowball colluded with Mr. Jones and attempted to sabotage the Battle of Cowshed. Squealer's lie is so fabricated that even Boxer questions it. When Boxer recalls that Snowball was given 'Animal, Hero, First Class' immediately after the battle, Squealer insists he has secret documents to prove Snowball was working with Mr. Jones. Squealer uses Boxer's illiteracy to his advantage to manipulate him. Boxer then mentions that Snowball was wounded during the battle, and Squealer comments that it was arranged for Mr. Jones to inflict a flesh wound. Squealer then goes into great detail about how Napoleon saved the day. When Boxer still doesn't believe him, Squealer appeals to authority by saying that Napoleon initially announced this information. After Boxer accepts Squealer's story, Squealer threatens the animals by saying,

I warn every animal on this farm to keep his eyes very wide open. For we have reason to think that some of Snowball’s secret agents are lurking among us at this moment! (33).

In Chapter 9, Boxer is sent to the knackers. Squealer tells the animals that Napoleon paid extra money to send Boxer to the veterinarian. Squealer then announces three days later that Boxer died a peaceful death. Squealer cries and says Boxer's last words were,

Forward in the name of the Rebellion. Long live Animal Farm! Long live Comrade Napoleon! Napoleon is always right (49).

Then, Squealer's mood changes as he fabricates a believable story that a veterinarian actually purchased the knacker's van. Later that night, Squealer and the other pigs drink whiskey and party.
Orwell presents Squealer in a negative light by illustrating his ability to fabricate believable lies, manipulate history, and use logic to outsmart the other animals. Squealer is also insensitive and dangerous. He feigns tears and uses the animals' emotions to manipulate them.