Diehards rhymes with:
blowhards, backyards, bankcards, blowhards, bodyguards, boulevards, courtyards, datacards, flashcards, graveyards, hildegardes, junkyards, lifeguards, lumberyards, mastercard's, mastercards, postcards, safecard's, safeguards, scorecards, shipyard's, shipyards, stockyards, sungard's, vanguard's
Diehards sounds like:
dardis, dart's, dartez, darts, darty's, derides, derthick, deteriorates, detritus, detroit's, dirt's, diuretic, diuretics, doddridge, dordies, doritos, dorothy's, dortch, dreads, dredge, dredges, drudge, druids, duarte's