Ollie Watkins, Raheem Sterling, and Tyrone Mings scored the goals as the Three Lions cruised to a 3-0 victory, but the game was tarnished by the angry greeting that Manchester United star Harry Maguire received.
Southgate conceded that the 29-year-old had not been enjoying himself at Old Trafford this season, but he was visibly enraged to hear England fans booing their own player in the stands.
It appeared that Southgate was also implying that some supporters are being swayed by social media, or even by former players who are working as pundits.
Southgate was cited by BBC Sport as saying: "The response was a laugh, an absolute joke." Southgate added:
Harry Maguire has struggled for Manchester United.
No one, in my opinion, stands to gain from it." As he said, "Either we're all in this together or we're not."
The majority of them, I'm sure, wouldn't even know what to say if you asked them why they did what they did." Mob mentality is at work here. It wasn't everyone who tried to get his name sung, but there was a fanatical bunch at one end of the field.
"Players will take a look at that and wonder if it's me in the picture." As a result, players are less likely to show up. As John Barnes has previously stated, this has occurred in the past.
Harry's performance is critical for us." The World Cup will not be won by an army of players who have only three or four international caps between them. In the history of the game, something like it has never occurred."
"He's in an England shirt, and not only should you support a player in an England shirt anyway, but when you've played at the level he has for us – and put in the performances he has - it should be a total commitment behind him," he continued.
"To be honest, his performance was almost faultless. He had a key role in both goals, stepping out from behind for the first and being a key contributor to the second. The team has come together as a whole. We understand that everyone goes through difficult times, but he's a good player, and he'll be fine in the end.
Some are genuine England supporters, while others are persuaded by whatever factors are at play - social media or players who have played in the past who are influencing public opinion." In spite of the fact that he's playing for England, his club position is clearly problematic.
The booing of a few players in an England shirt was something I recall from decades ago, and it was never acceptable to me. "Fans should constantly rally around their favorite team."
Also, Jordan Henderson and Jack Grealish, both members of England's World Cup and Euros winning squads, took to Twitter to express their shock at the booing of Harry Maguire by England fans.
"I'm still trying to wrap my brain around what transpired at Wembley Stadium tonight. Harry has been a colossal force for the United Kingdom. It would have been impossible to make the improvements that we have made over the last two tournaments without him," Henderson added.
For no apparent reason, he was booed at his own stadium." What have we turned into as a species? Tonight's events were very unacceptable. I'm grateful to share a dressing room with him since he's someone I aspire to emulate. "We're all in the same boat."
Asked about Harry's contribution to the national team, Grealish said, "The World Cup and the Euros, he has been magnificent."
When he drives the ball forward, the first goal is scored; when he drives a little further, the second goal is scored." That is not the case with every central defender."
Alphonsus Odumu 3 d
Southgate
Maguire