No one said there was anything wrong with using a PRB. Heaven knows I killed my share of deer with them too. But if you have a sidelock with a 1:28 twist, the PRB probably won't shoot a PRB worth a darn. But in a 1:66 or 1:70 twist, the same can be said for the saboted bullet or conical.
So the debate is actually - If you have a sidelock, should you use a PRB. Most of us say definately not. It should be dependant on what your rifle shoots best.