It’s tempting to guess that if the principal characters in “Love Is Strange” had not been so naïve, they wouldn’t be wrestling with the difficult situation they find themselves in.

A self-conscious, tentative drama, “Love Is Strange” concerns George and Ben, two New York City men who have been together for 39 years. When the state of New York passes a law allowing same-sex marriage, they quickly make their union legal.

John Lithgow stars as Ben, the older of the two. Alfred Molina, giving a substantial performance in a lightweight drama, co-stars as Ben’s younger partner, George.

“Love Is Strange” opens at the best of times for George and Ben. Approving family members and friends happily assemble at Ben and George’s wedding. After saying their vows, the newlyweds, together at the piano, entertain the guests.

But there’s something amiss straight away. Molina’s George is so obviously faking it at the keyboard. This may seem a minor detail, but George happens to be a high school music teacher.

The religious affiliation of the latter high school sits at the crux of “Love Is Strange.” It’s a Catholic school.

George and Ben must have known that the Catholic Church doesn’t approve of same-sex marriages. Yet when the school principal tells George that his employment there must end immediately, the suddenly ex-music teacher is shocked. Everyone, George protests, including the students’ parents, knows that he and Ben have been together for years.

“The bishop wasn’t happy,” the principal, who’s also a priest, informs George. The principal expresses a small degree of sympathy but also cites the Christian witness statement that George signed when the diocese hired him. With George out of a job and Ben, a failed artist, apparently incomeless, the newlyweds must sell their apartment. The joy they experienced by marrying turns to misery. They’re forced to move in with friends and family and, in doing so, live apart.

As George and Ben sputter unhappily along, so, too, does the movie. Marisa Tomei co-stars in the thankless role of spouse to Ben’s nephew. Tensions grow when Ben moves in with them and their hateful son, 16-year-old Charlie.

Despite the tearful embrace by Ben and George that comes following trying days for the both of them, “Love Is Strange” usually keeps its emotional distance. The film is also missing pieces that would have made transitions to this or that scene smoother and more coherent. Mundane dialog drags it further down. Worst of all, the plodding “Love Is Strange” is just boring.