[Avodah] Vegetarians

[torahmike at gmail.com]

<continuing from Areivim>

 Whilst on the subject of Tzaar ba'alei chaim, can anyone explain the
gemora on BavaMetzia 85a, that
says Rebbe was punished for telling a fleeing korbon, to go be a korbon?

 I never understood this gemora- What exactly did he do wrong? What
should he have done? Tzaar baalei chaim isn't classically understood
to require one
to not kill an animal just because it doesn't want to be killed.

 Thanks!

      Mike