Goalkeeper Donovan Ricketts was given his marching orders after 34 minutes after showing his fist to Shrimpers fans, but the Bantams turned in a backs to the wall performance to deny Southend hopes of a first win in five matches.
Bradford should have taken the lead on 16 minutes through Dean Windass who rose to head Marc Bridge-Wilkinson's free-kick from the right but saw the ball rebound off the crossbar only for Ben Muirhead to blaze his follow-up wide.
The game settled into a stalemate before another Windass lay-off found Steven Schumacher who rifled a 30-yard shot low into the bottom right-hand corner of Darryl Flahavan's goal after 33 minutes.
Then the fireworks really started as Ricketts received his marching orders from referee Paul Armstrong for goading the Southend fans behind his goal.
Minutes after Windass took over between the sticks, Bantams manager Colin Todd was banished to the stands following an exchange with fourth official Simon Beck.
Windass was lucky not to be punished for fouling Freddy Eastwood in the box on the stroke of half-time.
But the stand-in keeper was beaten in first-half injury-time when Mark Gower floated his free-kick from the left over the two-man wall and into the top right corner with Windass rooted to the spot.
Anyone expecting Southend to run riot in the second half against 10 men were left disappointed.
The Bantams defended in numbers throughout the half as their switch to wing-backs provided Windass with plenty of protection.
The Shrimpers enjoyed plenty of possession but could not break City's rearguard down with most of their shots going wide.
And when Gower and substitute winger James Lawson did manage to get headers on target, they found veteran striker Windass well placed to save their efforts.