One of my friends once said “At least you didn’t be diplomatic.”. It somehow felt a little unsettling. Is “didn’t be” acceptable? Is it grammatically correct?
Most verbs in English form the negative in a strange way:
You jumped -> you didn't jump
You saw -> you didn't see
using the infinitive form ("jump", "see") and an auxiliary verb ("do", for example).
But a few special verbs (auxiliary verbs) form their negative in a different way by adding "not"
You were -> you were not = you weren't
You should -> you should not = you shouldn't
You were -> *you didn't be
You should -> *you didn't should
Perhaps if you read very old things, you find that even normal verbs used to do it this way
You jumped -> you jumped not
She loves me -> she loves me not