The Scottish international produced a textbook goal after Neil Warnock's promotion favourites had carved out the better chances in a highly charged encounter.
Sunderland, after a stuttering start to the season, have now won seven of the last nine games leaving Warnock's side facing testing games again West Brom, Wigan and Reading in the coming weeks.
United's top scorer Peter Ndlovu hit a crisp right-foot shot from a tight angle, stopped at the near post by Mart Poom and striker Ashley Ward went close with a fierce strike from 15 yards, turned away by the Sunderland keeper as United carved out a couple of early chances.
Argentinian defender Julio Arca weaved his way past three defenders as Sunderland broke quickly, but dragged his shot from just inside the area over the bar. The little full-back went even closer in the 15th minute cleverly deceiving Rob Kozluk only to pull his left-foot strike inches wide of the far post.
England Under-21 midfielder Michael Tonge almost broke the deadlock in the 34th minute with a twisting run from deep inside the Sunderland half, his vicious shot deflecting off defender Gary Breen and almost dipping underneath the bar.
Tonge then went close with a free-kick curling towards the far corner before Darren Williams steamed in to head the ball across the face of the goal for another United corner.
Sunderland snatched the lead six minutes later Stewart providing the cross as Kyle stepped in front of his marker beating Paul Gerrard from five yards.
Tonge almost snatched an equaliser in the 74th minute after Arca had been booked for foul on Ward. Tonge slammed a free-kick from the edge of the area which Poom failed to hold but as the ball spilled towards Paul Peschisolido the Sunderland keeper pounced to grab it at the second attempt.
Sunderland were reduced to ten men in the 85th minute, Arca being red-carded when he pulled back Peschisolido after picking up a caution 13 minutes earlier.