Earlier quoted context omitted.
Even the latter isn't contempt. I feel like I don't understand why anyone is interested in watching sports (as opposed to playing), but I certainly don't look down on them for it. At the very least, I know enough people that I respect that are into pro sports that it would be inconsistent to think something like "people who are into pro sports have nothing better to occupy their time and their minds".
It is contempt. It implies that there is no valid reason for liking X. You may not look down on them but when someone says "I don't see how anybody...", that is contempt. Not understanding is vastly different from expressing disbelief that anyone would do a particular thing.
This is completely wrong. You're essentially saying here that "I don't understand the valid reason for X" necessarily means "therefore X has no valid reason". I really hope you're just confused here, as opposed to actually believing this line of thought and applying it to things in general. To use my example again, when I say "I don't understand the appeal at all", I'm literally saying that _I_ don't understand it: I assume there's just something I'm missing about pro sports or some as-yet-unknown difference in my preferences that makes me averse to watching it.