They will go after him because if they don't "police their mark", anyone else could start using it.
"Trademark owners have a duty to police their mark. This applies to all types of marks – brand names, slogans, color, product shapes, or even a smell. The cost of dropping the ball on this duty can range from a bar on future enforcement of your rights against a particular company to a complete loss of all trademark rights. As a practical business reality, the value of marks that are not policed and their associated goodwill are always in danger.
This duty includes policing (1) for unauthorized uses of a mark, (2) for uses of confusingly similar marks, and (3) uses by approved trademark licensees."
https://natlawreview.com/article/primer-policing-your-trademark
That’s a good point. Go get him, Mets!