Overall, Shakespeare’s sonnets have a fairly ambiguous view of sex. For example, the famous Sonnet 129 is probably the most anti-sex poem ever written in the English language. What about Sonnet 137? Where does it stand? Well, it's kind of upset at sex to be honest. In light of the other themes we’re considering in this section, like lies and deceit and betrayal, the poem uses metaphors that describe sex as downright ugly and nasty—like when he refers to the "bay where all men ride," or the "wide world’s common place." Is this just sour grapes? As we all know from Sex Ed class, promiscuity can be risky. From this perspective, the speaker’s reference to a "plague" in the final line might just express his very reasonable fear of contracting an STD from his lecherous lady. Still, we think the main emotions are probably anger and disgust at being sexually betrayed.
The speaker is both sexually conservative and progressive. On the one hand, he supports the traditional view (conservative) by attacking a woman who is sexually promiscuous. On the other hand, he portrays a man—himself—who seems to want to be sexually monogamous (progressive!).
The speaker’s statements about sex in this poem have nothing to do with morality. Nope. He's taking a dip in Lake Me. This is all about his own personal feelings.