The problem is that what is a “seemingly innocuous” topic for one person can be, for any one of a number of reasons, a really important or hot-button topic for another.
Take something like tipping. For some people, it’s just a question of whether you leave 12% or 15 or 20, or whether you should leave it on the credit card or in cash. For others, it’s a moral and/or a political issue closely tied to broader questions of labor relations, a living wage, and the importance (or otherwise) or adhering to social customs that are not legally mandated.
Similarly, the question of declawing a cat holds very different levels of importance for different people, depending on where they stand on certain questions of human responsibilty for animals, animal rights, cruelty, etc., etc.
I think the examples given in the OP are good ones, in that they show topics that really don’t mean very much, in the big scheme of things. At least not to me.
At the same time, though, i can see a survey over wearing shoes in the house turning quite easily into a debate over the extent to which other people’s customs should be respected, etc., etc.
We need to realise that not only do we all have our own opinions on certain things, but that just because something is of merely academic or curiosity value for one person, this isn’t necessarily the case for someone else. I don’t think i’ve ever gotten involved in the whole circumcision debate, for example, and i really don’t have very strong feelings about it one way or the other. But i realise that other people do feel strongly about it, and that their strong feelings shouldn’t be ridiculed or dismissed out of hand just because i don’t happen to be very interested in the topic.
But it is still an objective fact that Showgirls blows chunks, while Starship Troopers is an allegorical masterpiece. And don’t even get me started on The Fourth Man. 