Can sweat kill you?
There is a lot of misinformation regarding winter damage to carbon frames. whether it is winter or summer you still need to keep your bike clean. If you leave ingress on your bike after a wet ride then that can eventually cause problems. It is not only specific to winter
Granted grit is only used in the cold months but as long as you are sweating over your frame on the turbo you are doing the same as you would on a winter ride. Wash it down and remove the salts. Salt eat at the cable stops and gets under the lacquer on spots where the lacquer is compromised. The good news is it can not penetrate the carbon itself
So ride the bike you love through the winter and into the warmer months. Well maintained carbon bikes are fine in all weather.