If Donald Trump had been a tennis player, he would have been Jimmy Connors. Brash, bombastic, bullying, bludgeoning anything in his way, swollen with entitlement, constantly grabbing his crotch to assert his manhood. If there had been such a thing as Twitter in the 1970s, Connors would have set it on fire. I hated him.

Well, I suppose I didn’t hate him, exactly. But I certainly very badly wanted Arthur Ashe to beat him on 5 July 1975, in the final of the Wimbledon men’s singles. In fact I wanted Ashe to humiliate him in the way that, a year earlier, the 22-year-old Connors had humiliated the 39-year-old Ken Rosewall with a 6-1, 6-1, 6-4 destruction that denied the great Australian the one major title he was destined never to capture.

With a display of phenomenal tactical discipline, playing a kind of Zen tennis, Ashe duly obliged. My virulent dislike of Connors promptly drained away. After that I couldn’t have cared less about him. But for a while I had experienced the sort of animosity that is increasingly evident among tennis fans, and from one quarter in particular.

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When Andy Murray took over the title of the world’s No1 player in the ATP rankings for the first time last weekend, displacing Novak Djokovic, who has held the top spot for 223 weeks over the past five years, some of the Serbian player’s fans responded with the aggression that has made them notorious among the British media in recent years. “What a truly sad day on planet earth. Murray and No 1 in the same sentence just doesn’t feel right. I am crying,” one of them wrote on Twitter. He or she followed up: “Who knows Murray outside UK? He’s definitely the most unpopular No1 for some time.” Another: “Rafa, Fed injured. Nole in a bad form and easy draws …”

Below the line, the arguments were intensely passionate and sometimes well informed, often delving into the minutiae of the ATP points system. Under a piece by the Daily Mail’s tennis correspondent, someone writes: “World No 1 with only three grand slams at the age of 30… Nadal has been injured for half his career yet still won over 10 slams.” (Murray is 29 and Nadal has won 14 grand slam tournaments, but let’s not worry about the details.) There is also an outpouring of abuse. “You sound like a bitter and jealous person,” one poster is told. “Get a life” is a common refrain. A senior tennis correspondent is brusquely advised to retire, having committed the crime of admiring Murray’s achievement.

This one is typical of the Djokovic fans who refuse to accept Murray’s right to usurp their hero’s place: “He’s not up there with ND. Not even close. ND is so far ahead of him that comparisons between the two are insulting to ND. Andy Murray is Djokovic’s personal toy. ND does with his toy whatever he likes. In the early part of his career Djokovic was a bit soft on his friend. But as he’s grown older he’s realised there’s no reason for him to be so nice, so he’s put his foot down and bashed Murray just about every time they’ve played in the last couple of years.”

Football was always tribal, but the back-page headline, the TV camera and now social media have transformed other sports into battlegrounds between those whose support of one side now automatically entails the denigration of opponents. Where batsmen walked and Stirling Moss once lost his best chance of the world championship by defending Mike Hawthorn, his rival for the title, at a stewards’ hearing, now sledging is a way of life and Lewis Hamilton and Nico Rosberg barely acknowledge each other as they wait to mount the podium.

But it still seems strange and incongruous that the game of Rosewall, Maria Bueno, Manuel Santana and Evonne Goolagong – not to mention John Betjeman’s Joan Hunter Dunn, immortalised in A Subaltern’s Love Song, a hymn to the home counties (“Miss J. Hunter Dunn, Miss J. Hunter Dunn/Furnish’d and burnish’d by Aldershot sun/What strenuous singles we played after tea/We in the tournament – you against me!”) – should be the focus of such bile, of such a readiness to write off the opportunity to enjoy it in all its dimensions.

There is an example of how this can affect otherwise rational people in Federer and Me, William Skidelsky’s book about his obsession with the Swiss champion, published this year. “A blot appeared on the otherwise sunny vista that stretched before Federer in 2004-06,” Skidelsky – a former literary editor of the Observer – writes, “and it took the form of a preternaturally muscled Spaniard. Like most diehard Federer fans, I loathe Rafael Nadal. I cannot stand the man or his tennis. In my more reflective moments, I am capable of admitting that this attitude falls short of perfect objectivity. Nadal, I am prepared to concede, may not be a wholly despicable human being. But no amount of ordinary decency can make up for the grave offence that he has committed, and continues to commit, simply by existing. This alone is enough to make him loathsome, unforgivable.”

Well, it’s a point of view, although it seems to me that such an approach inflicts serious collateral damage on an ability to enjoy the game to the full. Later in the book, leaving the pre-Wimbledon grass-court tournament in Halle, Skidelsky encounters another Federer fan, a Brazilian woman in her sixties called Marcia with “short, purple-rinsed hair, a battered face, sad eyes”. When the subject of Nadal is raised, she says: “How I hate that man. How I loathe him. He is not as nice person. He is a cheat. Always talking about his injuries. Always using the time out. But it’s not just that. It’s also his game. He only does one thing. He has no variety.” The author is sad when his companion reaches her stop: “I would have liked to have carried on talking to Marcia.” Not many of us would say the same, except in the cause of research into sporting pathologies.

Most tennis fans realise how lucky they are to have been living in the time of Federer, Nadal, Djokovic and Murray, the finest era in men’s tennis since that of Rosewall, Hoad, Gonzales and Laver. For the rest: give your heart and loyalty to one of them, by all means, but don’t let partisanship obscure the fact that each of them could not have done it without the others. And try to enjoy it all.