Former Black Cats midfielder McClean celebrated in front of the travelling fans and was confronted by Danny Graham and Lee Cattermole.
McClean claimed he was 'hung out to dry' by Sunderland over his decision not to wear a Remembrance Day poppy on his shirt during a game against Everton in 2012.
It was a flashpoint in an otherwise dull game as Sam Allardyce took charge of Sunderland for the first time, but could only watch in horror as his goalkeeper tossed away what would have been a valuable point at The Hawthorns
Pantilimon dropped a Chris Brunt cross to allow Saido Berahino to seal a 1-0 win and leave Sunderland rooted in the Barclays Premier League's relegation zone.
In contrast, victory lifted Albion seven points clear of the bottom three and lifted any early-season pressure on boss Tony Pulis
Defeat only underlined the size of the job Allardyce has to keep the Black Cats in the top flight as he watched them match the Baggies for much of the game, only to be undone by a mistake.
Boaz Myhill saved well from Billy Jones in the first half, but Pantilimon's gaffe was in keeping with a scrappy, uninspiring match which was littered with mistakes
Allardyce recalled Younes Kaboul and Sebastian Larsson for the suspended Sebastian Coates and Jeremain Lens while Jordi Gomez also got the nod.
Stephane Sessegnon was handed a surprise start for the hosts, having not even played a league game for the Baggies since April.
The Black Cats celebrated their 136th birthday on Saturday, but have been showing their age following their constant relegation struggles.
Allardyce, their eighth manager in the last six years including caretakers, has been parachuted in to save them from the drop, which has seemed inevitable for the past three seasons.
He got an immediate reaction, though, with the Black Cats comfortably the better side in the first half.
Cattermole and Steven Fletcher both had shots blocked before the visitors were denied by Myhill's brilliance.
Yann M'Villa and Fletcher were involved in keeping the ball alive in the Baggies' box before Myhill produced a superb reaction save to turn Jones' six-yard header over.
It was, though, the only moment of quality during a turgid first half which only lived up to the pre-match billing.
Sunderland kept Albion contained with their midfield strong and organised, giving the hosts little opportunity to break through.
Craig Dawson ballooned a shot into the stand nine minutes before the break to sum up the lack of quality, with only Sessegnon a sporadic threat with his direct running for Albion.
But nine minutes after the re-start the game sparked into life thanks to Pantilimon's clanger.
The keeper came out to claim a routine cross from Chris Brunt under the slightest pressure from Berahino.
But the Romanian dropped the centre on to the back of John O'Shea's leg and it ran for Berahino to poke in from three yards.
It sapped the confidence from Sunderland and, while M'Vila tested Myhill from distance with 13 minutes remaining, there was little fightback.
West Brom were allowed, without serious scares, to see out the game and left Allardyce in no doubt about the size of the task he faces
And after the final whistle McClean celebrated in front of the visiting fans and had to be pulled away by Craig Gardner after being confronted by several Sunderland players.
Source : PA
Source: PA