I would absolutely boo the anthem if we were playing somebody in a World Cup semi or whatever. Hostile atmosphere, maybe their players would feel a bit intimidated.
If I was at Spurs' new stadium, relaxing in the cheese room, and they started playing "Ozzie's on his way to Wembley" or whatever the fuck their songs are then I would also boo the shit out of that.
Actually do Spurs even have a song? Like we have Bubbles, Millwall have their own kind of knock off version, Everton have Z Cars. I guess Spurs have their own version of Southampton's song? It's a clever adaptation, if nothing else.