Walter Benjamin, who teaches religion at Hamline University, has boiled over on this page about one of those can-you-believe-it? newspaper reports: a committee has voted 10-8 to scrub ''Onward Christian Soldiers'' from the planned revision of the Methodist hymnal.

Millions must have snorted with contempt, as I did. But Benjamin took action. He shot to his typewriter and roundly denounced those sniveling committees that squeeze the rich Old Testament juices out of Protestant hymn books, reducing them to ''liturgical pabulum.''

And as for the post-Vietnam tendency to read soldiers, Christian and otherwise, out of the human pale, ''hymnal revisers,'' Benjamin says, ''should realize that the soldier as barbarian is an image, not a norm.''

Benjamin says many other sound and satisfying things: that Holy Writ, whence most good hymns derive, is sometimes a mixed and bloody matter (see the adventures of Kings Saul and David) and that heroic behavior ("the heroism of Achilles and Hector'') is at the core of our literature.

All true; wish I'd said it myself. Yet Benjamin's roar of outrage, while satisfying, left me with the feeling that something was missing.

Such as the real issue?

Admittedly, the idea of bumping a classic like ''Onward Christian Soldiers'' arises from confusion about the morality of warfare and is simply ridiculous. Unless millions of Methodists follow their committee around this mindless bend, the expurgation stands about as much chance of success as the Washington Monument does of being shut down in a budget squeeze. And anyway, don't the words speak of marching ''as to,'' not ''off to,'' war?

The recent revisers of the hymnal I occasionally sing from, the new Episcopal Hymnal 1982, have chucked James Russell Lowell's popular ''Once to Every Man and Nation,'' annoying many who identify it as a powerful anthem of Christian social responsibility.

Lowell apparently wrote ''Once toju . . ." in a white heat of antislavery outrage. Unfortunately, the mark of those origins lies heavy upon it. The world of 1845 appeared to Lowell one of absolute, clear-cut, one-time choices between ''the good and evil side.'' (So much for the rumor of God's measureless patience with sinners.)

The issue is whether a hymn offers heroic uplift or sound teaching.

The same must be said of the martial hymns that fret and divide Prof. Benjamin and the Methodist revision committee. What, exactly, do they say? However nobly rhymed or stirringly scored, if a hymn were built around the refrain, ''Saul has slain his thousands and David his tens of thousands,'' it would be thought to fall somewhat short of acceptable Christian attitude today.

The sensed mandates of a religion evolve, and boundaries of taste and sensitivity shift. There was a time when our slaveholding ancestors belted out hymns whose words seem to us today clearly incompatible with slavery. Yet they seem to have felt that holding other people as property was not only not un-Christian but a performance of Christian duty. Warring in the name of the Lord, in this age of ayatollahs and nuclear weapons, isn't so unambiguously jolly as it must have seemed to a 12th century Crusader.

"War,'' says Herman Wouk, ''is an old habit of thought, an old frame of mind, an old political technique, that must now pass as human sacrifice and human slavery have passed.'' Wouk is no pacifist. That the writer of some of the best American fiction about war should state his hopes in just that way makes them the more arresting. And if Herman Wouk can muse adventurously about the future of war, maybe hymnal revisers may do so as well -- so long, of course, as they don't commit ''liturgical pabulum.''

Meanwhile, if God's stomach were as queasy as 10 members of that Methodist committee seem to imagine, He would have called off the human experiment in disgust eons ago.