A perplexed John Longmire has questioned the thinking behind the boos that accompanied Lance Franklin in Sydney's 29-point loss to Collingwood.

The Sydney coach was baffled at the section of Collingwood fans who booed Franklin's every touch, in the first time the Magpies have hosted the Swans at the MCG since Adam Goodes was racially abused in round nine, 2013.

Superstar Franklin had 13 disposals, kicked a behind and didn't give away a single free kick.

"Charlie (Gardiner, head of footy) and I actually didn't know, we were on the bench and we don't sit back and sit there like a spectator, and didn't understand it," Longmire said.

"Why would they boo him? Why would you boo him?

"(You'd) probably celebrate a 36-year-old, wouldn't you, who's been a champion of the game? Why would you (boo)? It's been 10 years since we've played Collingwood here, why would you boo one of the champions of the game? It doesn't make sense to me."

Magpies coach Craig McRae was supportive of his counterpart and Franklin.

"I've said this before, I'm not a boo-er, we don't boo at home. You pay your money, you do whatever you want. I must admit I didn't hear it, I had my headset on, but we just don't boo," he said.

Watch the full post game press conference below.