Well, by that logic you could also condemn the converse situation - that no Mac case should have to be subjected to hosting PC innards. I don't see either situation as an indignity to the Mac.
Personally I think any such Mac-PC transplant hack (either way) is fine. But if you look at the situations where Mac folks have gotten upset, it's been when someone has gutted a perfectly good Mac in order to put PC innards in it. Putting Mac innards in a PC would seem to be a nice bit of poetic justice - especially to further prove what we Mac folks already know, namely that older Mac boards are far more useful than PC boards of a similar vintage.
M