It is usually the ones that you know have either never been to Anfield or even been to Liverpool, proper roll your eyes moment when somebody says that.
It is used to justify their existence, instead of somebody just simply nodding and going OK, they are hoping for a 'wow, you are a Liverpool fan, I like you as this defines who you are and you must be a wonderful person for not only being a fan of a club but a massive one'.
To be honest and not just saying this but if I was on one of these shows and they asked hobbies, etc. I would simply say I liked watching sports, wouldn't even mention football never mind a specific club, unless they asked.
Was he a massive Tranmere fan though