A designer welcomes criticism.
No code of ethics should protect your work from criticism, be it from clients, the public, or other designers. Instead, you should encourage criticism in order to create better work in the future. If your work is so fragile that it can’t withstand criticism it shouldn’t exist. The time to kick the tires on your work comes before those tires hit the road. And be open to that criticism coming from anywhere.
Criticism is a gift.
The role of criticism, when given appropriately, is to evaluate and improve work. Criticism is a gift. It makes good work better. It keeps bad work from seeing the light of day.
Criticism should be asked for and welcomed at every step of the design process. You can’t fix a cake once it’s been baked. But you can increase the chances your project is successful by getting feedback early and often. It’s your responsibility to ask for criticism.