"You're nuts" said by Crooks to Lennie. Derogatory because there's a lack of understanding towards people like Lennie.
'Lennie covered his eyes with his huge paws' Described as an animal, specifically a bear which connotates to being childlike and innocent.
'ketchup' doesn't have any complex thoughts whatsoever and he gets judged for it.
'I didn't wanna hurt him' is big physically but mentally is delicate and frail. Shows that there are still people with pure thoughts in a world full of migrant workers.
'Lenniebleated with terror' Lennie is vulnerable and unaware of his physical strength. So he is an easy target