A Man for All Seasons doesn't deal with marriage in a domestic way, but it's super concerned with marriage in a political way, and the action of the movie is set in motion by the marriage that King Henry desires with Anne Boleyn.
Thomas can't approve of this marriage—which is a political marriage designed to produce a heir and prevent civil war—because he would have to ditch the Pope and the Catholic Church in order to do it. More's marriage with Alice provides a good counterweight: It's an example of a marriage that is a genuine union.
Questions About Marriage
Is there anything wrong with the new marriage Henry wants to contract? Think about the effects that failing to produce a male heir would have on the country—specifically, civil war.
How does Thomas More's marriage to Alice function? Is it similar to a "good" marriage in the present day?
In the movie, the Pope has to approve King Henry's divorce and remarriage. In the present day, how has the relationship between marriage and religious institutions changed?
Chew on This
It's wrong to marry or get divorced for political reasons like Henry VIII—a marriage should be a genuine love-match.
If you actually consider the position of king in the 16th century, it's simply necessary for him to marry for political reasons. Everything a king does is inherently political, and he has greater social responsibilities to think of (like having a clear successor in order to prevent civil war). There's just no way around it.