But football is also a uniting force. This may be lost on my American friends, but after all, it is - by far - the world's most popular sport.
Last night at Wembley Stadium, the sight of the England and France teams, their managers, national administrators, an heir to the throne, and 71,000 fans, standing together, put some much-needed polish on the beautiful game.
Against the backdrop of Friday's terrorist attacks - which included three attempted suicide bombings during the France-Germany friendly at the Stade De France - yesterday evening's demonstration of la solidarité showed that could suspend the petty rivalries that make for semi-amusing in-game banter, and come together for something more altruistic.
The camaraderie of internationals and club teammates alike, the joint singing of Le Marseillaise by both sets of fans, and the impeccable observance of the minute's silence, will live on in the memory for years to come. And there was more poignancy in the game's 57th minute when France's Antoine Griezmann and Lassana Diarra came on as subsitutes. Diarra's cousin Asta Diakite was killed in the attacks, Griezmann's sister was caught up in the carnage, but escaped unharmed.
However, while liberté, egalité and fraternité flowed freely through north-west London last night, 500 miles away in Hannover there had been a stark reminder of the dangers ahead for football: a "concrete" - though now discounted - security threat at the HDI Arena forced the Germany-Netherlands friendly to be abandoned less than two hours before kickoff.
For the organisers of next summer's European championships in France, the country's status as a target for home-grown terrorists, not just imported from Belgium and Syria, will be now become an even bigger headache than previously imagined.
France has very publicly declared itself "at war" with those behind Friday's attacks, and the country remains under a state of emergency. Not surprisingly, however, UEFA and the French football authorities have been at pains to point out that security preparations for Euro 2016 have been ongoing for some time, with the kick-off just seven months away.
Already on Saturday, the president of the Euro 2016 organising committee, Jacques Lambert, said the tournament was now at "tangible risk", but added that the Charlie Hebdo attacks in January had upgraded the risk from being simply "theoretical".
"It doesn't probably change much for the security professionals regarding preparations of the event," he told French radio station RTL, "but you see that for everyone, public opinion, media, teams, it adds a special intensity."
No kidding. The fact that at least one of last Friday's bombers at the Stade de France had a ticket will be even more worrying. At the very least, it demonstrates the extent of the terrorists' planning and thinking, but at least investigators will have 79,000 ticket sales that could be useful.
Scanning the hundreds of thousands of tickets that will be sold for next summer's tournament will not be so easy. Indeed the provisions for security at all ten Euro 2016 stadia will come under increasing public scrutiny given the spread of arrests being made in France of terror suspects and their supporters.
Questions will be raised about the level of police and military presence in the host cities, security in the fanzones and the team hotels and training camps, how public transport is made safer without it grinding to a halt, and the issue which is already raging about border controls throughout the European Shengen Area.
Of course, this climate of fear is exactly what the jihadists will want: "Wondering whether Euro 2016 must be cancelled is playing the game of the terrorists," Lambert told RTL. "We will make the decisions we need to make so that the Euro finals can be held in the best security conditions." France, he said, had included the terror risk in their original bid to host the tournament, submitted in 2009. That, though, had obviously been in the context of a general threat. Since Friday, the threat has mutated to one in which extremists have deliberately targeted a football match on French soil.
Noël Le Graët, president of the French Football Federation, has admitted that Euro 2016 is now looking far more high-risk than it did before Friday. "You can see very clearly the terrorists can strike at any moment,” he said at the weekend. "There was already a concern. As of now, it is clearly even stronger."
Almost imediately after Friday night's attack, UEFA issued a statement - quite correctly - that Euro 2016 will go ahead as planned. More than 1.5 billion Euros have been invested in the stadia - the Stade de France and Parc des Princes in Paris, the Stade Vélodrome in Marseille, Stade des Lumières in Lyon, Stade Pierre-Mauroy in Lille, Matmut Atlantique in Bordeaux, Stadium Municipal in Toulouse, Stade Bollaert-Delelis in Lens, Allianz Riviera in Nice, and Stade Geoffroy-Guichard in Saint-Étienne. But, of course, you can't put a price on human safety.
During the London 2012 Olympics, much was made beforehand of mitigating the terror threat by installing anti-aircraft missile batteries on East End tower blocks, deploying Typhoon jets at Northholt Aerodrome, and placing a SAS team on alert within the British capital. And that was just for one main stadium and a handful of satellite venues.
Even with the French police and military, with battle-proven, state-of-the-art intelligence-gathering technology, being applied to combat ever-evolving and sophisticated terrorists, the risk heightening far beyond "significant" will weigh on the minds of the teams and fans already planning their summer of football in France.
Football fans are a resilient bunch, if a little rough around the edges. Without being flippant, they endure the ups and downs of their clubs and national teams, usually with good humour. The Portsmouth fans seen singing "Stand up if you hate ISIS" on Saturday were well meaning, if in possession of somewhat misplaced irony. However, dealing with the very real threat next summer will take more than shaven-headed bovver boys in Kappa rollnecks chanting "come and have a go if you think you're hard enough!".
It's going to take an unprecedented effort by governments, the intelligence services and the police to ensure that terrorists, to recall the IRA's chilling statement after the 1994 Brighton bomb, do not get "lucky" a second time. As they said, "You will have to be lucky always."