That's your answer.
Even if the alcohol didn't harm the yeast, it would evaporate when you bake the bread, so you don't need the alcohol component(painful to say such a thing).
Heat the whiskey first to evaporate the alchohol. That will leave the water and flavor behind. You'll need more booze than your recipe calls for as you'll lose volume as the alcohol evaporates. 80 proof, you'll lose about 40%.
How do you know when you've evaporated the alcohol? It will boil off at a lower temp(173 degrees) than water(212), so(for all pracitcal purposes) the alcohol will be completely gone before the water starts to boil. I you have a thermometer you can use, bring the heat up in the whiskey slowly. You'll see it boil at 173. When it stops boiling and the temp starts to climb again you are done. (If you keep the heat on it will rise to 212 and begin to boil again as the water boils off.)
For the small amount of whiskey I assume you'll use it would be difficult to monitor with a thermometer. If you can get a test tube, put the whiskey in that and suspend it in a water bath and heat the water. Watch for the whiskey to boil (it will happed before the water starts to boil) and take out the test tube when the first boil ends.
Oh, hell...that's a lot of bother. Just send me the whiskey and I'll do it for you. If you need a 1/2 cup or so, just send me a fifth(I'll need to practice a bit to get it just right) - Bushmills 16 would be an excellent choice.