After he shoved him, he repeated what Caleb said to him: "Motherfucker". Somehow, Canelo took this as a literal slur on his mother(language barrier?). Whether you believe that reason or not(not sure I do), it was just a shove either way. That happens a lot in boxing face-offs.
Plant got humbled either way. He was the one who took a swing outside of the ring. He doesn't seem that likeable to me anyway. Like most PBC fighters, he seems to be full of shit, when he's talking to the press or on sounding off on social media.
I think the shu was because Caleb was being too cocky on the stage and had been mouthing off on social media, calling him a cheat among other things, which annoyed Canelo. That said, Canelo served his ban and people forget he willingly took the hair follicle test which a truly dirty fighter have avoided like the plague. --There's a lot more skin heads in boxing than there used to be too, funny that-- That test can show drug use for up to 12months later, so his result proved that however it ended up in his system, there was no long term use(which would be dangerous anyway... heart problems) and it also proved there were no other banned substances in his system either(steroids cycling theory debunked). He took that test without hesitation and certain people want to over look it, as well as pick and choose when VADA can be trusted.
Caleb himself, is on the outspoken Victor Conte's "SNAC" program. The same person, who in 2005, admitted to running a doping program for many athletes for many years, none of which were caught at the time or known about until he implicated them. Of course, he says athletes on his current "SNAC" program are clean and everything is legal but would it really surprise anyone, if we find out he's cheating the system again? That's the energy these people who buy the narrative Caleb was pushing, have towards Canelo and the Reynoso gym but they don't keep the same energy for others which shows their lack of objectivity and their bias.