Montpellier thrash Racing after Bismarck brawl
The game was marred by a fist fight in the warm-up as Montpellier forwards Bismarck Du Plessis and Mohamed Haouas came to blows, exchanging several punches before teammates dragged the raging pair apart.
"In the good old days, it sometimes happened like that in the locker room, it shows that it means something to the players," said former Scotland boss Cotter.
Captain Louis Picamoles added: "These are things that happen, but there's nothing nasty. We are a group that gets on well, but sometimes it boils over a little and it's settled between men."
After the pre-match fireworks, Montpellier set about keeping top spot as two tries from Jan Serfontein either side of the break and another from his South African compatriot Nico Janse Van Rensburg saw the home side run away with it by the 45th minute.
They had gone in at half-time 13-3 up thanks to two penalties from Ruan Pienaar, with Pat Lambie's firsthalf penalty earning the visitors their only points of a long, hard afternoon.
Later tries from Fijian wing Timoci Nagusa and Picamoles sealed a win that ensures Montpellier will emerge from the weekend top of the heap.
Montpellier lost at Agen last week and had seen the Parisians close the gap on them, but Saturday's mauling leaves the home side on 66 points with six matches to play, while the visitors are on 58 and can be replaced in second spot by Toulouse, who play Lyon on Sunday.
Later on Saturday, struggling champions Clermont edged to an 11-9 win at Brive to move up to ninth, although they remain 12 points off the top six and a play-off spot.
Toulon ran in eight tries to hammer Agen 54-5 and move level on points with Toulouse.
Former France international Vincent Clerc scored the opening try in the eighth minute to equal former Montpellier winger Laurent Arbo's French top flight record of 100 tries.
Bottom club Oyonnax continued their recent revival with a third victory on the spin by winning 26-20 at Bordeaux-Begles, taking advantage of bigger sides missing internationals during the Six Nations.
Pau scratched out an 18-15 victory over La Rochelle, the club's sixth win in a row, but one that potentially came at a steep price as former All Black Colin Slade was stretchered off early in the second half.
Montpellier 41-3 Racing92
Pau 18-15 La Rochelle
Bordeaux 20-16 Oyonnax
Toulon 54-5 Agen
Brive 9-11 Clermont