When Lear runs into Gloucester in Act 4 scene 6, he is clearly mad. His crown is made of weeds and wild flowers. In his babbling he confuses his audience and makes sense at the same time. He refers to Gloucester by the sins (adultery) he has committed. He says that Gloucester's son, conceived in an unlawful manner, treats his father better than his daughters, who were conceived in marriage.
I pardon that man's life. What was thy cause? Adultery?
Thou shalt not die: die for adultery! No:(125)
The wren goes to 't, and the small gilded fly
Does lecher in my sight.
Let copulation thrive; for Gloucester's bastard son
Was kinder to his father than my daughters
Got 'tween the lawful sheets.
While Lear has pardoned Gloucester's sin, his rant shifts from adultery to his issues with all women and sexuality. As his monologue ends, he has spouting nonsense and runs away when Cordelia's men come to get him.