I love the first season of The Flintstones. It's really uneven but they snuck in some weirdness before the Hanna Barbara fun police started mandating boringness.
I don't know, this would have to be the one and only case of lewd content in a "Flintstones" cartoon, and even then it's kind of out of nowhere. I am thinking this is a joke so poorly conceived and executed that the helpless viewer desperately tries to find meaning where there is none.
Someone pointed it out before that Barney was talking about his wife Betty as his second head. Makes a lot more sense, but isn't as sensational as assuming DICKS DICKS KIDS CARTOON DICK JOKE.