Yes because it damages one's own morals and can increase the likelihood in the future to be the one to exploit "suckers" for profit.
We can still say "I told you so" and have sympathy. But we shouldn't throw the sympathy away in contempt. Another reason is that over our life at least once we will be the suckers, and will look on those who said "i told you so" and see contempt in their eyes. Is that what we want?
I have sympathy for the 1% of people whose response to "Hey I think having these devices is a really bad idea because you can never be sure where the audio is being sent and who's listening" was "You raise a good point, I won't be buying it" or "Thanks for pointing that out, that sounds scary but I trust them".
As opposed to a dismissive "I don't care", "I have nothing to hide", or "You're being paranoid" of the other 99%. Those people either don't need sympathy because they don't feel wronged, or don't deserve it because they shot the messenger.
We can still say "I told you so" and have sympathy. But we shouldn't throw the sympathy away in contempt. Another reason is that over our life at least once we will be the suckers, and will look on those who said "i told you so" and see contempt in their eyes. Is that what we want?