From reading this thread and the bug, it sounds like there is one key issue installing something new on build machines.

As discussed before in regards to python, there was a desire not to go above a certain version so that the tiger build machine could run a script. That seemed reasonable to me.

Similarly there is a desire in this case to avoid Ruby because it means installing something new on other build machines. This also seems reasonable to me.

There are other issues that seem tangential which are being brought up and only confuse the subject for me:
It probably didn't help that the subject of the email focuses on languages in a highlander smack down style as if there can be only one.

Focusing again, given the build machine issue:

dave