The NBA has been VERY consistent on this rule over the years. It might, in fact, be the single most consistently enforced rule in the entire league. Been an absolute black and white issue for years and years. Nothing has changed. Not the first time its come into major play in a series either.
It is the least gray of all their rules. Created to deter bench-clearing brawls. I don't think it has done so, necessarily. There is no more than one real brawl per year and the rule itself was established (way back in 93) w/ the NY/Phx brawl.
Note how many times NY is on this list.
93 - Knicks / Suns (KJ vs Doc Rivers, Greg Anthony comes in swingin)
94 - Heat / Hawks (playoffs, Grant Long & Doug Edwards vs Keith Askins)
94 - Knicks / Bulls (playoffs, Derek Harper vs JoJo English, spills into front row)
96 - Kings / Pacers (Michael Smith vs Dale Davis, 16 suspended)
97 - Knicks / Heat (playoffs, P.J. Brown flips Charlie Ward, Ewing/L.J./Starks/Houston susp'd)
98 - Heat / Knicks (playoffs, Zo vs L.J. & Van Gundy)
01 - Spurs / Knicks (Marcus Camby tries to knock Danny Ferry's head off)
02 - Lakers / Bulls
03 - Kings / Lakers
03 - Blazers / Warriors (Bonzi vs Chris Mills, fans throw trash at Blazers, Sheed takes it to GS lockeroom & bus)
05 - Pacers / Pistons
07 - Nuggets / Knicks