This has happened to me a few times, in bigger or smaller scale, and I think it happens to many of us.
We as designers have the pleasure/curse of leaving quite a bit of us in every design.
When you have a client who, you feel, undermines your design decisions, how do keep that from affecting what you are doing?
Related question: How can I work with a client that doesn’t know what they want?
You have a “thumbprint” client. This person must always change something, and feel like he’s left his thumbprint on it, or he doesn’t think he’s done his job correctly.
I have a coping strategy I got from When Bad Relatives Happen to Good People. It’s called “Setting a Budget.”
A woman was upset because every time she went to her son’s house for a weekend visit, things went wrong, plates were broken, the grandkid had a tantrum, clothing was ripped, etc., and the woman was miserable.
So the counselor asked her how many things usually went wrong in one of those weekend visits. “Oh, at least two dozen,” she said. So the counselor told her to reset her expectations and budget for 24 lousy things to happen. After 24 lousy things, then she could be justified in being upset, because 24 lousy things was the norm.
The very next visit the son was astonished at how relaxed the woman was despite the chaos. “Oh, only 12 lousy things have happened, so I’m well under budget,” she told him.
To apply that here, figure out the average number of thumbprints (changes) your client usually makes, and set that as your budget. Go in with that expectation.
After that number of changes, then you can justifiably feel frustrated or undermined.