The Workplace Stack Exchange site would be a suitable site to post such a question, but I feel whom better to ask such a question than other graphic designers.
I'm sure most of us have had to deal with co workers or clients that are keen to alter your design and question your ability to design as well. It would seem that our industry is more prone to interference and interrogation, when the same people wouldn't dream of telling those other professions how to do their job.
I've had a few scenarios recently where I've been tempted to seek advice here on how to deal with it and stand my ground, but would seem off topic. What are your thoughts on this?