  It has been suggested a long time ago by W. Bardeen that non-vanishing of the
one-loop same helicity YM amplitudes, in particular such an amplitude at four
points, should be interpreted as an anomaly. However, the available derivations
of these amplitudes are rather far from supporting this interpretation in that
they share no similarity whatsoever with the standard triangle diagram chiral
anomaly calculation. We provide a new computation of the same helicity
four-point amplitude by a method designed to mimic the chiral anomaly
derivation. This is done by using the momentum conservation to rewrite the
logarithmically divergent four-point amplitude as a sum of linearly and then
quadratically divergent integrals. These integrals are then seen to vanish
after appropriate shifts of the loop momentum integration variable. The
amplitude thus gets related to shifts, and these are computed in the standard
textbook way. We thus reproduce the usual result but by a method which greatly
strengthens the case for an anomaly interpretation of these amplitudes.
