Spanish golfer Gonzalo Fernández-Castaño has brutally compared 2019 TIME Person of the Year Greta Thunberg to Adolf Hitler in a bizarre series of tweets on Friday.

Thunberg is a world-renowned environmental activist, who has campaigned for greater action to combat climate change. The Swede made headlines in August by sailing to New York City for climate conferences, choosing not to fly in hopes of reducing her carbon footprint.

After Thunberg was announced TIME’s Person of the Year on Thursday, becoming the youngest person in history to do so, Fernández-Castaño posted a map on Twitter detailing his flight paths from 2019.

“Another year in the books! Enjoy @GretaThunberg,” Fernández-Castaño posted.

The 39-year-old also shared a graphic detailing the amount of CO2 and methane the planes ejected during his flights.

Fernández-Castaño inevitably faced some backlash, but doubled down on his criticism of Thunberg by comparing the 16-year-old to Hitler and Joseph Stalin.

“So what? Adolf Hitler was @TIME Person of the Year in 1938. So was Stalin, not once but twice,” Fernández-Castaño posted.

So what? Adolf Hitler was @TIME Person of the Year in 1938. So was Stalin, not once but twice. — Gonzalo Fdez-Castaño (@gfcgolf) December 13, 2019

Previous winners of TIME’s Person of the Year include American Presidents Barack Obama and Donald Trump, along with Mark Zuckerberg and Vladimir Putin.

The accolade is awarded annually to a person or group that “for better or for worse … has done the most to influence the events of the year”.

Fernández-Castaño has been a professional golfer since 2004, with eight professional wins. He currently resides in Florida in the United States.