Green’s Dictionary of Slang

to become very angry; thus rear-up, an argument.

1921		N&Q 12 Ser. IX 385: Rear Up. To get angry.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 237: Rear Up, A: A row. Quarrel. Noisy argument.
1981		T. Wilkinson Down and Out 168: He had been thrown out [...] because he had ‘reared up’ on a man who complained about his snoring.
1996		Sun. Times 24 Nov. n.p.: Sean Duigan, his former press secretary, says he ‘reared up’ when it was suggested that he donate the money [...] to charity [BS].