Plymouth chairman Paul Stapleton's extraordinary midweek outburst against Holloway fuelled a red-hot atmosphere.
And Halmosi ensured Argyle fans were in full voice when he swept home Lilian Nalis's clever pass.
Home keeper Luke McCormick saved well from Matty Fryatt and Gareth McAuley late on as Argyle held on to win.
Plymouth manager Paul Sturrock:
"We were determined that this game would be about football and not Ian (Holloway), and we achieved that and got the result we wanted and deserved.
"Our keeper was magnificent in the last 10 minutes when they had about six forwards on and he did well to keep a clean sheet.
"Hopefully now this will give us a bit of belief because we worked hard, kept our shape and deserved the win."
Leicester: Alnwick, James Chambers, McAuley, Kisnorbo, Clapham (Fryatt 89), Hume, Oakley, Clemence, Bori (Campbell 46), Hayles (Laczko 65), Howard.
Subs Not Used: N'Gotty, Kishishev.
Booked: Howard, Hume, Laczko.
Plymouth: McCormick, Connolly, Timar, Doumbe, Sawyer, Abdou, Paterson, Nalis, Halmosi (Hodges 80), MacLean (Fallon 85), Easter.
Subs Not Used: Wotton, Mackie, Jutkiewicz.
Goals: Halmosi 34.
Ref: Iain Williamson (Berkshire).