Ronald Koeman's visit to Anfield on Saturday was not well received by Everton fans
The Merseyside derby is known by some as the friendly derby
This is due in part to the fact that many families in Liverpool are split down the middle with Liverpool and Everton fans and, as such, it'd be really weird if they just outright hated each other.
It sometimes extends to proceedings on the pitch, with the derby noticeably less vicious than others which take place.
That doesn't mean the fans like the opposing team, or even tolerate them, as Ronald Koeman learned on Saturday.
Yes, Ronald Koeman, that Ronald Koeman who was criticised by Everton fans for placing red baubles on his Christmas tree when he was manager of the club.
Now manager of the Netherlands, Koeman was present at Anfield for Saturday's 5-1 demolition of Arsenal, presumably to watch two of his most important players: Georginio Wijnaldum and Dutch captain Virgil Van Dijk.
He was present with his sons and, as most people do on a nice day out, documented it with a photo which he posted on his official Instagram account.
— Ronald Koeman (@RonaldKoeman) December 29, 2018
Koeman could have reasonably expected that the comments would range from "what a game!" to "enjoy your day", and certainly not being told that his sons were ugly, but that's what happened.
That is because, you see, Koeman's Instagram comments were quickly seized upon by Everton fans, who deemed the former manager's attendance at a rival team's stadium an act of heresy.
It is all absolutely ludicrous of course, but also quite funny and above all proves that football fans will never, ever stop being entirely ridiculous.