I think it's fair to say that everyone who watched the January 18th, 2014 game against the Flames, which started with a line brawl, was left wondering "what the &^@# brought that on!?"
In an interview with Dan Murphy, Tom Sestito claims that having Kellan Lain in the line-up was the catalyst for the brawl:
https://www.sportsnet.ca/hockey/nhl/murphys-mailbag-canucks-better-defensively-sutter-ferland/
I have no idea if Sestito's version of events is accurate but there you go.