He should probably stop, as it is not seen as professional.
Is it a big deal? No. But he should refrain or just one of the female fighters will dislike it and make a public comment leading to a row.
Is it a big deal to me, personally? No. Not really.
Is is a big deal in the contemporary Western workplace? Yes. Today it absolutely is.
I work for an international financial corporation based in North America. It employs close to ~20,000 people. In November, 2019, ALL management (that is a LOT of people) had 3 days of mandatory training regarding corporate culture and workplace conduct.
One of the major discussion issues is touching in the workplace and apparently, it is being outlawed. No touching, no hugs, no nothing. Violations must be reported. This extends to social events. I shit you not, this is the direction we are headed in.
“The conduct could be unwelcome and make the recipient uncomfortable. It exploits a power imbalance the recipient may be afraid to challenge and may be construed as bullying or sexual harassment [etc. etc.]”
So... a large male boss/authority figure running around kissing female employees 1/3 his size on the head...? Those days are over come 2020. It is straight-up insane how much and how quickly the workplace is changing.
Do I think this nonsense is getting out of hand? Yes. But it is still happening...