It's perfectly fine to be Packers fan, but I would judge a person who showed up to a wedding or funeral dressed as a cheesehead.

Nitpick on wording: I wouldn't call wearing a suit to a wedding “looking like a non-Packers fan” -- it's not like non-Packers fans are all that much more likely to do so than Packers fan; I'd call it “not looking like a Packers fan”. By the same token, on hearing “looking like a non-nerd”, I think about an appearance that's significant evidence than you're not a nerd; I'd refer to an appearance that doesn't provide much evidence one way or another as “not looking like a nerd”.