The song, by the Statler Brothers, is here.
I don't think defining religion as a perspective on ultimate reality is uninteresting or useless.In particular in America one of our guiding concepts is keeping matters of religion free of compulsion. Some people on the atheist side want to engage in what I consider to be compulsion, but this often tries to fly under the radar because on the face of things it isn't religion. But, in the sense that matters for things like the Establishment Clause, atheism is very much a religion.
For example, it is hypocritical to use the Establishment Clause argue against the teaching of intelligent design on the grounds that those who advocate it intend to undermine materialism and support religious belief, but not use the Establishment clause to argue against the use of evolution to attack religious belief and promote materialism.