i keep my tank at 77-78
thinking about it, when i was in hawaii, the surface temp was about 81degrees when we snorkeled. most of the fish we keep were 10-15 feet below the surface, where the temp is cooler. i even have a pic of a moorish idol approx 35 feet below the surface, where the temp is much cooler.
i wouldn't see the harm in keeping a 75deg tank, as long as you take that into consideration during acclimation
just my opinion