They're supposed to get branding perfect before launching a pre-beta signup form? What if they don't get the necessary traction, investment or licenses? Sounds like a terrible waste of money and bad prioritization for a startup in their situation.
Disputing feedback when people give it is a surefire way of making sure that no feedback is given in the future.
When I see constructive feedback, I'll take that into consideration.
Does that make his observation invalid?
It's not an observation, it's an opinion, and definitely not an inarguable one.
Branding is as important as product or software development for startups. I'm not talking about selecting cool colors, having a nice logo or tagline, but purposely making strategic marketing decisions so that it's not left to chance or, even worse, your competitors.