I completely disagree.  Samwise keeps his word, but does not swear an oath.  He says that if Frodo does not come back, neither will he.  Sam does not swear an oath, yet his aide is key to the final act in the quest.  I'd like to distinguish the difference of saying you will do something, and following through with your word, and 'swearing'.  I had no idea that Quaker's thought swearing oaths was a horrible thing, I just go by what I read in biblical texts.  Warning against swearing oaths is mentioned twice, once in Matthew 5 and once in James 5.  Jesus himself gave the warning originally, and so he obviously thought it was a serious enough thing to teach.  The Rohirim's noble deeds could have happened with or without their oaths, yet they lived in a society in which vows were an everyday part of their culture, just as vows in medieval culture were an important part of their every day life.  Tolkien deals with oaths both as a very real part of society, and as a potentially dangerous thing.  The oath is not WRONG so to speak.  It is not a sin in itself, however going back on your word is wrong.  Taking an oath can show very good intentions, and dying for the cause is also a very noble thing to do.  I would argue the ACTION is important, not the oath.  It is important for a person to do what they say, it is not necessary for them to swear that they will do something.  Keeping your word is of utmost importance, but as a mortal who does not have 'foresight', an oath could turn into something that  ends up being morally wrong.  Feanor kills many innocent people, even his own kin, for the sake of his oath.  His sons refuse to give up their oath and face the consequences, and so bring pain and misery on the peoples of Middle Earth.  Gollum did not have any idea that when he swore to keep the ring from "Him", he would be sacrificing himself in the fires of Mount Doom.  He did not take the oath for noble reasons.  He even shows his character as mostly evil with a small portion of good still left in him.  He meant to be the ruler of the ring himself, having no idea where the oath he swears on the ring will take him.  Gandalf says in the Fellowship, "'But you cannot see very far . . . . Neither can I." (87 in my version), indicating a Hobbit's inability to see the future, and the 'big picture' as far as Iluvatar and the Valar are concerned.  For Frodo to swear an oath to take the ring to its doom, he very well could kill off entire races, trample over his friends, even do something that was morally incorrect, because situations change, unexpected things happen, and in order to fulfill your oaths sometimes you have to do evil.  Saying you will do something and remaining faithful to your friends and allegiances, that is noble.  However, I do admit that the Old English societies represented in the texts placed a high importance on vows of service, some of which were oaths, but not all.  Of course people who break their oaths are punished, thus is the nature of the oath.  It does not mean that the 'higher powers' in the book think that it is a wise move, however as Iluvatar says, all things work for His glory no matter what 'folly' His children perform.  I hope this clarifies my opinion on his works.