Maybe I'm just not getting the British. I know these characters use the noun "rot" to mean bullshit. Here's the Oxford English dictionary definition #5:
slang. Ridiculous or nonsensical talk or ideas; nonsense, rubbish. Also: pointless or fatuous activity. Also as int. Cf. tommy-rot n. at Tommy n.1 Compounds 2.‘Rot!’ say I scornfully. It's the mark of bad writing to bolster your saids with adverbs, I say scornfully, brain-rottedly. Now, where are my cigarettes?
1846 Punch 10 136/2 Peel and Potato-blight defy To make him hold his tongue, or try To talk aught else but ‘rot’!
1857 T. Hughes Tom Brown's School Days i. vi. 138 Let's stick to him, and talk no more rot.
1879 M. E. Braddon Cloven Foot iv. 96, I thought he despised ballet-dancing. Yet this is the third time I have seen him looking on at this rot.
1889 tr. R. Shilleto New Triposes in C. Whibley In Cap & Gown 228 Your Natural-rot, your Moral-bosh.
1894 G. Moore Esther Waters xxxix. 302 All bloody rot; who says I'm drunk?
1914 G. B. Shaw Fanny's First Play 158, I quite agree that harlequinades are rot.
a1953 E. O'Neill Long Day's Journey (1956) i. 35 It's damned rot! I'd like to see anyone influence Edmund more than he wants to be.
1977 C. McCullough Thorn Birds ii. 36 ‘What if it isn't the Eyetie girl?’.. ‘Rot!’ said Paddy scornfully.
1990 R. Clay Only Angels Forget vi. 78, I insisted on a church wedding. Mother said, ‘What rot, Isobel, you don't believe in any of that’, which was true but irrelevant.
2004 A. Hollinghurst Line of Beauty iii. 78 He talked a lot of rot at dinner on... the coloured question.