The message of Megillas Rus, take 1:
Ploni Almoni knew that Boaz, the Gadol haDor, paskened that Rus the Moavi’ah was permitted, but Ploni nonetheless stubbornly stuck to his own way of thinking. No matter what his reasoning, whether it was concern for the established custom of rejecting converts from Moav, or worry lest a future Beis Din disqualify his lineage, of some other concern, Ploni was still wrong. His decision cost him the opportunity to bring David's family into the world. The message of the megillah is that personal cheshbonos, even when they appear to be well grounded, must give way to the rulings of our Gedolim.
The message of Megillas Rus, take 2:
The established norms of tradition could not be clearer: converts from Moav could not be accepted. Social and religious convention closed minds and hearts to Rus' plight. But there was someone willing to listen – Boaz. Roused by empathy for her plight, Boaz re-examined accepted doctrine and discovered that the law was not as clear as some would like it to be. There was room for leniency – Moavi v’lo Moavis – and Rus could be accepted into Klal Yisrael. Accepting Rus would be perceived as the act of a maverick, but Boaz did not hesitate. The message of Rus is that when faced with the call of those who cry out for empathy, for equality, for help against injustice, we must re-examine tradition and find innovative solutions, even if they challenge convention and received wisdom. The Ploni Almoni’s of the world may lead a life of safe complicity, but it is the courage of Boaz (Bo-Oz) that will lead us to redemption.
The message of Megillas Rus, take 3:Be wary of simplistic derush that imposes ideological readings onto the text to the preclusion of other possible meanings.