I thought Dave Pallone was the first? He wrote a book and without naming names, he had an affair with an A-list movie and tv star who made it big in a couple of musicals (grease, urban cowboy, i read between the lines).
He was “outed” in 1988 and quit.
The timing is different I believe. He left baseball as an ump and then admitted his preference. This column is from 1988 and titled “Resign Now or Be Fired, Pallone Told”:
http://articles.latimes.com/1988-09-20/sports/sp-2428_1_umpire-dave-pallone
During his time in the majors, Pallone was often among the lowest-rated umpires in the NL.
Pallone admitted an ongoing dispute with Cincinnati’s Dave Concepcion that began in 1983 and confessed he sometimes tried to block the infielder’s view. Last year, Pallone ejected Concepcion for arguing a called strike but later acknowledged, “I missed the pitch.”
Pallone also had a disagreement with then-Montreal pitcher Jeff Reardon, who said the umpire threatened to “bury” him. Pallone denied making that remark.
Several years ago, Pallone publicly said he had run up a gambling debt of more than $1,000 while betting on sports events other than baseball. It was never alleged Pallone bet on any baseball games, although his gambling drew concern from baseball officials.