>If you toss a rock in Western Europe, you’ve got a better chance of hitting a football fan than someone who wants to go bouldering or train for a marathon.

Yes and no. If you HAVE to choose a specific hobby, football will have more chances than others; but it will still work in a minority of cases and assuming carries an implication.

A comparison I could make is starting a conversation in the US with 'did you watch fox news yesterday?'. Out of all channels, it's the most watched one; but you still have high chances of asking a non-viewer, and then get hit by negative connotations.

Personal hobbies are much better topic for various reasons (you don't assume, people will naturally be exited about discussing their own, etc).