Complex sentence: Although taken aback by his forced retirement, he at the time laughed down the case against him: when it was made known that the Ministry purge was directed against "homosexuals and drunks", he jokingly retorted that his alcoholism was public knowledge.
Split into simpler sentences: Although taken aback by his forced retirement, he laughed at the case against him. When it was made known that the Ministry purge was directed against "homosexuals and drunks", he jokingly retorted that his alcoholism was public knowledge.