Myles Weston had given the Gills a 42nd-minute lead but Padraig Amond was caught by goalkeeper Stuart Nelson seconds after coming on as a second-half substitute, Nelson saw red and sub 'keeper Tommy Forecast's first job a minute later was to pick Beattie's spot-kick out of his net.
It had looked good for Martin Allen's pace-setters when Weston struck three minutes before the interval, with both sides having previously enjoyed chances to open the scoring. Danny Jackman's looping cross found the striker, who turned in the area and fired home through a crowd of bodies from eight yards.
After the break Stanley defender Toto Nsiala had to clear Adam Barrett's header off the line as the visitors looked for a second.
Stanley boss Leam Richardson had to change things in the 69th minute and he introduced Amond, who had an immediate impact as he was brought down when clean through and, after Nelson was given his marching orders, Beattie drew the Reds level.
Lewis Montrose had a chance to win it for 10-man Gillingham but his effort was cleared off the line by Rob Atkinson, while Craig Lindfield was clean through for Stanley but fired wide and Rommy Boco hit a 25-yard strike against the foot of a post in the last minute of normal time.