Named in late December as the new president of the Japan Broadcasting Corporation, known as NHK, he officially took over from his predecessor on January 25, and immediately triggered a diplomatic storm.
In a press conference set up to introduce the corporation's new head, the 70-year-old Momii began with a prepared statement. "I will do my very best to provide you with fair, impartial and accurate news coverage and high-quality programming of all kinds," he said.
Formerly an adviser to information technology company Nihon Unisys, Momii tried to play down concerns over his lack of experience in broadcasting.
"I believe that my experience, including working overseas and knowledge from my career in the IT industry, will help NHK to fulfil its role as a public broadcaster."
After that fairly promising opening, things went rapidly downhill as he attempted to answer questions from assembled journalists, who quickly sensed their subject was going to be utterly frank about the "fair, impartial and accurate" coverage that the national broadcaster would be providing.
Momii did not disappoint.
"It is only natural to clearly state that the Senkaku Islands [Diaoyu Islands] and Takeshima [Dokdo to Koreans] are Japanese territories," was the opening gambit, parroting the national government's position on Japan's two most immediate - and apparently intractable - rows over sovereignty.
His comments carried not even a hint of the impartiality and even-handedness that a media outlet needs to retain the sense that it is not simply a mouthpiece of the government.
The hole Momii insisted on digging for himself got deeper when he described the issue of "comfort women" forced into sexual slavery for the troops of the Imperial Japanese Army during the early decades of the last century as "puzzling".
"[The issue of] comfort women is bad by the morals of today, but it was a fact of those times," he said. "Korea's statements that Japan is the only nation that forced this are puzzling.
"'Give us money, compensate us' they say, but since all of this was resolved by the Japan-Korea peace treaty, why are they reviving this issue?" he added. "It is strange."
Momii dismissed other nations' criticisms by adding that brothels were "common in any country at war".
Not content with causing outrage in China and Korea, NHK's new president then managed to alienate a good proportion of his home audience by backing the controversial state secrets bill recently passed by Prime Minister Shinzo Abe's government.
Given that the bill had been passed, he said, "there is no point in questioning it".
NHK likes to compare itself favourably to the BBC and has ambitions as a global broadcaster on a par with the BBC or CNN, but Momii's nationalist agenda and unthinking support for the policies and attitudes of the government undermine its credibility and good name, critics say.
"He's probably not the best person to install as the head of Japan's national broadcaster, is he?" said Makoto Watanabe, a lecturer in communications and media at Hokkaido Bunkyo University.
"NHK should be like the BBC and although I accept that it would be hard to meet those standards, it should at least be substantially independent of any authority and interference from outside," he told the Sunday Morning Post. "And that should be the case even though it does rely on the government for funding and is under its supervision."
Watanabe said that, in fact, NHK has done "quite well" in maintaining its autonomy and editorial independence to date. But he fears that the appointment of Momii is a sign of things to come.
"This shows that Abe is intent on putting people who share his political ideologies into positions of influence, even if they have absolutely no experience or knowledge of the industry," he said.
Another such example was his appointment of Tsuneo Watanabe, the former chairman of the conservative Yomiuri newspaper, as head of the government's advisory council on protecting state secrecy.
"It's actually a bit embarrassing," Makoto Watanabe said. "I would say that the majority of people in Japan cringed when they heard Momii's comments. We know our national broadcaster should be independent - even mature - but it's clear that he is not able to play that role."
The government has nevertheless closed ranks around Momii, with Chief Cabinet Secretary Yoshihide Suga telling reporters that there was no need for the head of NHK to resign and that he made his remarks on the issue of wartime sexual slavery "as an individual".
Clearly someone in a senior position had made the government's displeasure over the international fallout clear, however, as Momii's second appearance in public was to apologise for his first.
Saying that his comments had been "extremely inappropriate", he added that he had been speaking in a private capacity.
"Even as an individual opinion, it is not something I should have said," he added. "It was my first time [addressing] such an occasion and I did not know the rules."
The apology for voicing personal opinions will do little to assuage anger at home and abroad; the opinions themselves were the problem. The greater worry is the degree to which they will be reflected in editorial policy.
Makoto Watanabe insists that questions must be asked over a system that permits the prime minister to appoint the 12 members of the board of governors of NHK who then, in turn, name the corporation's president for a three-year term.
"He was basically selected by the prime minister, meaning there is no independence or impartiality being exercised here," he said. "How dare Abe choose this man to control the face of Japan internationally?"
Famously not a nation to protest too vociferously, criticism of Momii's appointment has rumbled through Japanese society rather than erupted. He has weathered the initial storm, people say, but he will have to tread more carefully in the future.
There are already signs that NHK - whose corporate slogan is "Straightforward, earnest" - is pulling its punches on the issue.
Momii's comments warranted three paragraphs buried at the bottom of a news story about Abe being questioned by opposition politicians in the Diet about economic policy.
A poker-faced Abe replied to a question from Banri Kaieda, head of the Democratic Party of Japan, that he hopes the new NHK president and employees continue to be neutral and impartial and that they do not yield to political pressure.