It is amazing what certain events can do to bring people together, regionally and geographically. It's akin to people putting aside differences at weddings, funerals, etc., even if it put aside only temporarily.
Canada is so cup starved that from what I have seen in 30 years, people will put aside their differences and even hatred of certain teams to cheer for them as they are from Canada. For me, I hate the Leafs with a passion, BUT if it was the Leafs vs Dallas in the Stanley Cup Finals, you can be sure I would be rooting for the Leafs. Would not have a Leafs flag in front of my house like an Oilers one, but aside from stupid Boston Pizza commercials suggesting people get together and cheer on the Canadian team, I think many people were doing that. I know so many people at work and in my neighbourhood who are Habs and Leafs fans but Oilers gear because regardless of other differences during the season, the Oilers were Canada's team in these playoffs. If the sample size was the microcosm of online comments, that is not representative of what I saw in real life with a concerted solid support for the Oilers. I even have colleagues in Quebec who were wearing Oilers jerseys and rooting for the Canadian team.