Mentioning these sorts of concerns with other people in the company (especially higher-ups) is crucial. They can offer you the guidance on how to handle the situation far more effectively than some strangers on a forum.
I have had many instances of these sort of situations. Half the time you just suck it up and do it (if the person is more senior or it's a topic you're not so confident about) and the other half you can usually find some other strategy like meeting in the middle.
Maybe Celery is the best option? Have a team-wide meeting to discuss his side of the story. Sure, he might be one to just advocate constantly, but give him his pedestal to speak. If his arguments are shaky, he will step down from the pedestal on his own when he realises that this decision is inefficient and unnecessary. If he's not the founder/CEO then talk to the founder/CEO or anyone above this guy so that they can help you put him in his place.
Sorry I couldn't be of technical help but I hope this feedback will help tackle your team's root problem - communication.