Some — including Team Sky themselves — have pointed the finger at the media, who have whipped up fervour against a dominant rider threatening to run away with the Tour. Others say that Sky have themselves to blame for a clinical and even arrogant public face. Or is it, in fact, that Tour de France crowds love an underdog so much that they can't bear to look at a winner?
In the last few days, tension and doping accusations have intensified as the Tour enters its third week and the crucial Alpine stages. At the same time, incidents have happened on the road. A fan punched Richie Porte in the ribs on Tuesday, others spat on Porte and Luke Rowe, and one threw a cup of urine on Chris Froome on Saturday.
Though they are just a few bad apples among hundreds of thousands of spectators, it has raised the question: Do the French hate Team Sky?
'Sky looks like a big machine'
"The people are are suspicious of Sky," said Le Parisien journalist Lionel Chami, who has the vast experience of covering 30 Tours de France. He says that many people see the team's success as just too good to be true.
"They see the black bus, it's opaque. A few years ago, Sky came and shouted, ‘We're going to win the Tour in five years.’ They did it, twice. It's very impressive. But French people worry about that.
"The feeling was the same for Wiggins, except Froome comes after Wiggins. We wondered about Wiggins, coming from the track and becoming a thin guy. A year later, another guy does the same. It's a bit suspect."
For others, it's the sheer clinical professionalism of the team that raises antagonism.
"Part of it, Chris Froome is a Brit and Sky looks like a big machine," said François Thomazeau, a French freelance journalist now covering his 27th Tour.
And now, with Sky riders protected by increased security after the events of the last week, the situation is getting worse.
"Unfortunately, the greater police presence now won't favour Team Sky. It could look like VIP treatment, and it could be counter-productive," added Thomazeau.
"In a way, they may have lost their temper by responding to everything. It could have been better to play things down."
'Froome is too robotic'
"It's completely different from the USPS and Discovery Channel, but it's easy to make the comparisons between these teams and Sky," explained Gilles Comte of Vélo Magazine, a Tour journalist since 1992.
"Lance Armstrong is the recent past. And for the French public, Chris Froome looks a lot like Armstrong. He looks a little too robotic, and not Latin enough."
Chami says that the power of Froome's performances is being amplified by social media — and that can be poisonous.
"[Someone punching] is one idiot among 100,000 people," he added. "They are not cycling experts, they listen to media, social networks... They've been told what to think. And they worry when they saw Froome – 'Vrooomme!' – like on Ventoux and La Pierre-Saint-Martin."
'It's not Froome — it's the yellow jersey'
At the heart of the matter is perhaps a more simple explanation. Tour de France crowds love an underdog — and that rules out Chris Froome from the start.
"To be honest, they don't hate Froome," said Thomazeau. "It's not him, it's the yellow jersey. They have something against the leader. Even Jacques Anquetil was booed on the road, but they liked Raymond Poulidor. They like the losers more than the winners.
"There was a lot of hostility towards Armstrong— not just the yellow jersey, but because he was arrogant and American. Last year, of course there was no talk of doping with two Frenchmen in the top three. With all this background, you can understand.”
In the end, many people come back to the role of the media.
"Are certain media pushing it? Yes, probably," Comte continued. "Each family in France listens to France 2 TV, to Laurent Jalabert. If you say, 'You have questions about Sky,' then that's enough to introduce those thoughts in viewers' minds that he's a cheat."
Is the vitriol of the past week a result of the French public hating Chris Froome? That's too simple an answer. But while Team Sky's dominance of the Tour de France could put them in the history books for the third time in four years, it's proving even harder to win the love of fans by the roadside.
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