There is a common perception that religion is defined not so much by particular doctrines (like the existence of a god) or in particular functions (like providing a structure for morals) but instead by attitude. One of the most famous ways this has been expressed in theologian Paul Tillich's idea that religion and even theism is the focus of our "ultimate concern."
There seems to be a certain validity to this position because so much about religion appears to revolve around a person's attitude towards life, the universe, and what is most important to them. Does this allow us to conclude, then, that some great faith or concern qualifies not simply as an object of worship and veneration, but also of divinity and religion?
There is, of course, the obvious problem with the vagueness inherent in such a definition of religion. It seems to include so much under the umbrella of religion that little is left over - and if everything qualifies as a religion, then the term itself stops being very useful anymore. We already have other words we can use to describe the objects of our devotion and "ultimate concern," so why co-opt religion into this duty? Moreover, those of us with various forms of faith or ultimate concerns aren't likely to appreciate such conversion by redefinition.
Another problem lies in the fact that this broad definition appears designed to make religion seem appealing and pleasant. That in itself is not necessarily bad, but it fails to acknowledge the fact that not everyone has faith in good things and not everyone's "ultimate concern" is in that which is moral, kind, and just.
A good example can be found in some of the political systems which have caused so much death and destruction over the past hundred years. The best instance of that would probably be various forms of fascism, and Nazism in particular. All of them represented objects of great passion which people devoted themselves to, mind and body.
That's one of the fundamental problems with faith: there is no good way to restrict its object to the things which you approve of. Once "faith," whether focused upon an "ultimate concern" or not, is held up as a valid or even valued means for acquiring "knowledge" and a basis for living one's life, it just isn't possible to assert that the Christian faith is good, but the Muslim or Nazi faith is wrong.
Moreover, a person who accepts faith as the basis for their beliefs effectively gives up the means for critiquing the beliefs of others. A belief based upon faith is not a belief based upon reason, logic, and evidence. If a person is not going to use reason, logic, and evidence as standards by which they judge their own beliefs, then it would be hypocritical to try and use them as standards for judging or critiquing the beliefs of others.
Unfortunately, that doesn't leave much to use. If a person can't criticize the belief of another because it isn't consistent with logic or the available evidence, or because it is simply unreasonable, what else is there? How can a Christian who relies on faith criticize a Nazi who also relies on faith - by insisting that the Nazi faith is wrong simply because the Christian faith says so?
Granted, many people do good things because they have a strong faith in what is good and right, and this in turn provides a powerful set of motivations for them. At the same time, there are people who have a strong faith in what others would call evil - and that, too, provides a powerful motivation. In the end, it may actually be better in the long run if people have little faith in the good so long as they don't have great faith in the evil.