"I'm taking down his poster in my room when I get home and will replace it with one of Vladimir Kramnik"
If you wanted to, I think you would find much more examples of Kramnik being rude, and directly towards his opponents rather than towards some closing ceremony. I for example recall when he lost to Nepomniachtchi in the last round of the Russian Superfinal, and stormed off in anger
https://www.chess.com/forum/view/general/angry-kramnik
After Anand won the World Championship Kramnik said:
"he is always lucky a little, as I noticed. He played 1-1 with both 2nd and 3rd players and had no winning chances in any of these games, this is very usual for him"
You could find quite a few things that might make Kramnik sound as no less of a bad loser than Carlsen, at the linked occasion above he didn't even attend the closing ceremony :-)
hey!