Richard Grenell, the new U.S. ambassador to Germany, formally took up his post in Berlin on Tuesday and immediately got to work as Donald Trump’s representative by offending the German people with a tweet.

Grenell’s inaugural Twitter address to his hosts, a stern command to German companies doing business in Iran to obey the American president’s decision to sabotage the nuclear arms control agreement that opened the way for Western investment, or face U.S. sanctions, did not go over well.

As Germany’s leading financial daily, Handelsblatt, reported, the tweet drew thousands of comments, “many of them from angry Germans basically telling the ambassador, a longtime critic of the Iran deal, to butt out.”

Among the more temperate replies to Grenell’s tweeted threat was one from Wolfgang Ischinger, a former German ambassador to the United States, who advised the novice diplomat to avoid issuing “instructions” to his hosts.

Grenell’s comments sparked anger across the political spectrum. Fabio De Masi of Die Linke, a far-left opposition party, called on the German foreign ministry to make it clear to Grenell that his threats on behalf of “the arsonist in the White House” were inappropriate.

Germany’s finance minister, Olaf Scholz, reportedly pledged on Wednesday to protect German businesses working with Iran from potential U.S. sanctions.

In response to the wave of criticism generated by his tweet, Grenell suggested that he was just following orders and had used “the exact language sent out from the White House.”

It was notable, however, that America’s ambassadors to the two other European signatories to the Iran deal, Britain and France, issued no such warnings to companies in those nations.

Rolf Mützenich, an arms control expert from the Social Democratic wing of Germany’s governing coalition, suggested that Grenell appeared to be imitating his boss “in miniature,” through his use of Twitter as a battering ram.

That impression, however, is unfair to Grenell, whose reputation as a noted Twitter troll far predates his association with Trump.

Grenell, who once served the Bush administration as U.N. Ambassador John Bolton’s spokesman, was forced to delete hundreds of sexist, rude comments from his Twitter feed in 2012, during his brief tenure as foreign affairs spokesman for Mitt Romney’s presidential campaign.

The uproar over his tweets at the time, combined with anger from Republican homophobes who objected to the fact that he was gay, led to Grenell’s resignation from the Romney campaign just days after he had joined it.

In addition to mocking the physical appearance of female political figures, Grenell has frequently used his Twitter account to harass journalists, relentlessly accusing them of partisanship for any reporting that challenges the far-right ideas he promotes.

Rather than engage in dialogue, Grenell uses the platform to badger reporters whose work he dislikes to the point where many eventually tire of his inane arguments and block him.

He then proudly boasts of being blocked, as if goading journalists into disengaging with him to avoid his tirades was an achievement.

(In the interest of full disclosure, I am one of the legion of reporters who resorted to the block button to escape Grenell’s harassment. In my case, the final straw was his claim that, by sharing video of Richard Nixon bowing to Chairman Mao during the absurd controversy over Barack Obama bowing to another foreign leader, I was secretly working for the 2012 Obama campaign.)

Calling Grenell a troll is perhaps not entirely accurate, though, since his reputation for harassing reporters was well-established before the advent of Twitter. During his tenure as spokesman for the U.S. delegation at the U.N. members of the press corps described him to the Village Voice, in 2003, as “rude,” “arrogant,” “unbearable,” and a “bully.”

It is unclear what sort of vetting process Grenell went through before being dispatched to Germany as Trump’s representative, but the Germans should be braced for more confrontational behavior if his personal interactions with reporters are any guide. Irwin Arieff, who covered the U.N. for Reuters during the Bush administration told the Huffington Post in 2012 that his memory of Grenell was as “the most dishonest and deceptive press person I ever worked with.”

“He often lied, even more frequently offered half answers or withheld information that would weaken his case or reflect poorly on his ideological point of view,” Arieff added.

The new U.S. ambassador’s abrasive start to his tenure in Germany comes as that nation is searching for ways to keep the deal to constrain Iran’s nuclear program in place. According to Handelsblatt, German exports to Iran were worth $3.5 billion last year, and many of Germany’s biggest businesses are now working with the country.

In addition to Germany, France, Britain and the European Union helped to negotiate the deal with Iran, and are considering ways to keep it alive despite Trump’s threat to impose new U.S. sanctions on European firms that do business in Iran. One legal measure under consideration would be using an existing E.U. law to shield German, French and British companies from American sanctions.

Updated: Wednesday, May 10, 8:25 a.m. EDT
This post was revised to add a new headline, more tweets from Richard Grenell’s Twitter feed and to note his claim that his offensive tweet used language provided by the White House.

Top photo: During a ceremony in Berlin on May 8, 2018, Richard Grenell, left, shared a laugh with German President Frank-Walter Steinmeier. Grenell’s partner, Matt Lashey, looked on.