I agree with Roe, Surianne etc--I honestly had no awareness that microwave popcorn was even an issue til now. If someone had asked me, what's a universally stinky food that many people would object to, popcorn wouldn't even occur to me.
Sure, if an office wants to have a 'list of banned foods' that is totally their right. It might actually make sense in a small office where everyone is reasonable. Everyone gets to say 'I hate this food smell' and have that respected, so there ends up being a list of several foods not allowed but it's based off the preferences of those specific people, which is all that matters.
But I think the problem happens when there's an assumption that it is/should be widely known that certain foods are universally problematic.