Doesn't he realize that the term at its core refers to a female animal, and that using it as a term of derision indicates that the female of the species is a lesser creature than the male? When he calls Trump "a whiny little bitch" he is dependent on negative stereotypes of women for the "joke" to work: Trump is a lesser person than others because he exhibits characteristics of a whiny female, which is worse than a whiny male. Being female in and if itself makes you less than a male.
He is stuck in a 1960s attitude about sex. He sees transgender and gay rights as having to do with the sex act, not with sexuality. But then, he tends to see all male-female relationships and interactions as being based on the act of sex. That's why he continues to make jokes about sex in a way that most modern comedians have dumped as being disrespectful and ignorant.