It’s not as bad as your tv or your phone but it normalizes the practice. It also opens your local network to all kinds of vulnerabilities because of the world class level of quality and safety whatever smartness in the dishwasher was programmed with. And if it’s a smart anything, it probably comes with the app to make it work, which opens the gateway to our phone and its treasure trove of data.

So yeah I agree with your friends that data mining your dishwasher in itself is rather innocuous, but why allow it to happen altogether and open yourself to all the above?