I understand why this raises suspicion, but I think you should look further into intent. Was it to show what a good poet he is, or was it because of attraction or romantic interest? There are many roads that lead to Rome. Either may require a response from you, but the response may be different based upon intent.
I also wonder if he broke a prior agreement that sharing such things should not be done. I'm all about couple having negotiated ground rules for their relationship. Without that, one person's expectation can be violated by the other person who does not have the same understanding of a boundary. I find a lot of couples just live their relationship without having conversations about how their relationship will work on a variety of issues such as other people, faith practice, child rearing, finances, etc.