The question back at you, phrased differently; Could you live with engaging an armored active shooter and hitting and killing innocents, either from misses or pass thru?
Bit of a gray area there for me. I hope I never have to find out, either way.
The plain fact of the matter is that this is a risk we all assume every day we decide we're going to carry our chosen firearm.
And the fact that an active shooter may or may not be wearing armor makes not one bit of difference with this decision.
We each have to come to grips with this risk and make our own choices in the matter. And likewise, we'll each find out how we'll live with it if it ever comes to pass.
@RetiredUSNChief answered the question, nicely.