My cousin from Rome bought a half Barca half Spurs scarf when we went to watch the preseason game at Wembley a few years ago
One of his friends came over a few years ago and I took him to watch us play Birmingham - he loved the game and was really in to Spurs and all the songs, but - in the pub after the match some drunk guy actually wanted to fight him because his hat had an Arsenal badge on it (it was hat from a preseason tournament Lazio were in and had the badges of all four teams involved in)
Luckily I was twice the size of the guy and it was pretty easy to resolve the situation so it didn't detract from his enjoyment of the day but he didn't realise the relevance of the Arsenal badge on his hat (ironic since from my experience the rivalry between Lazio and Roma is actually a lot more intense and I'm sure if I wore a Roma hat to a match with him he'd expect there to be trouble)
One of his friends came over a few years ago and I took him to watch us play Birmingham - he loved the game and was really in to Spurs and all the songs, but - in the pub after the match some drunk guy actually wanted to fight him because his hat had an Arsenal badge on it (it was hat from a preseason tournament Lazio were in and had the badges of all four teams involved in)
Luckily I was twice the size of the guy and it was pretty easy to resolve the situation so it didn't detract from his enjoyment of the day but he didn't realise the relevance of the Arsenal badge on his hat (ironic since from my experience the rivalry between Lazio and Roma is actually a lot more intense and I'm sure if I wore a Roma hat to a match with him he'd expect there to be trouble)