This (heavily-ironic) quote from Stanley Hauerwas is fun:
One reason why we Christians argue so much about which hymn to sing, which liturgy to follow, which way to worship is that the commandments teach us to believe that bad liturgy eventually leads to bad ethics. You begin by singing some sappy, sentimental hymn, then you pray some pointless prayer, and the next thing you know you have murdered your best friend.
But, while bad liturgy may not lead to bad ethics in the crude way described by Prof Hauerwas (and the good professor has a point in telling Christians to get a sense of perspective), ethics should only be a secondary concern for Christians anyway. This is described well by Luther in the following statement (reference is given as WA TR 1:624; LW 54:110, for hardcore Luther geeks):
Doctrine and life are to be distinguished. Life is as bad among us as among the papists. Hence we do not fight and damn them because of their bad lives. Wyclif and Hus, who fought over the moral quality of life, failed to understand this … When the Word of God remains pure, even if the quality of life fails us, life is placed in a position to be what it ought to be. That is why everything hinges on the purity of the Word. I have succeeded only if I have taught correctly.
And the problem with bad liturgy – with “singing some sappy, sentimental hymn” and praying “some pointless prayer” – is that it obstructs (at best) the Word of God and distracts people from the gospel. “The purity of the Word” is not simply a matter of what goes on in the pulpit – it’s what goes on in the rest of the service, too.