It was pretty bad.
It all started when Montreal booed the American national anthem as a way to voice their displeasure to GWB and his decision to send troops to Iraq. But when the Leafs/Isles series started, their fans booed the everliving **** out of our anthem as a way to get "back at us"...even though Toronto had nothing to do with this. Even poor Jamie Lynn Siglar (Meadow Soprano) sang both anthems looked extremely uncomfortable while performing.
Circle back to Gm 3 in Toronto, and everyone at the ACC cheered the US anthem as a sign of respect and to show no hard feelings. But with that, coupled with the extreme amount of physicality and violence in this series, Isles fans couldn't let things go; they ended up burning not only Leaf jerseys, but also the Canadian flag in the Nassau Coliseum parking lot.
I remember the pictures in the Toronto Star vividly. Really took me awhile to forgive that fanbase...and this is why when Isles fan get on their soapbox to complain about us Leaf fans, that they really need to shut their ****ing mouths as they have nothing on us compared to what they've done!