Final answer:
Ponyboy's outburst towards Johnny is due to him being tired and frustrated, which occurs during a stressful situation and is not reflective of Ponyboy's true sentiments towards Johnny.
Step-by-step explanation:
The reason behind Ponyboy's outburst towards Johnny in 'The Outsiders' when he says, "An' you can shut your trap, Johnny Cade, 'cause we all know you ain't wanted at home, either. And you can't blame them," is primarily due to a) Ponyboy being tired and frustrated. This confrontation occurs in a moment of high tension and emotional turmoil for Ponyboy, which causes him to lash out at Johnny, despite their close friendship. The outburst is not a reflection of Ponyboy's true feelings; rather, it's an expression of the stress he's under.